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Index

• ( ) (parentheses)

• for functions, 22, 56, 101

• for tuples, 15

• * (star)

• in function arguments, 102–104, 108–109

• in module imports, 229–230, 240–241

• in variable names, 46

• operator, 5, 38–40, 47, 57, 298, 307, 310, 313

• ** (double star)

• in function arguments, 104, 108–109

• operator, 5, 40, 56, 57

• *=, **= operators, 7, 41

• + (plus sign)

• in file modes, 258

• in numbers converted to text strings, 250–251

• operator, 5, 10–11, 14, 38–40, 47, 57, 91, 298, 307, 310, 313

• += operator, 7, 41, 92, 111

• , (comma)

• in numbers converted to text strings, 250–251

• separating values, 276

• - (minus sign)

• in byte formatting, 253

• in numbers converted to text strings, 250–251

• operator, 5, 18, 39–40, 50, 57, 309

• -= operator, 7, 41, 92

• . (dot) operator, 56, 79, 154

• .. (double dots), in relative imports, 237

• … (ellipsis), in extended slices, 96

• / (slash)

• as path separator, 281

• in function signature, 105

• operator, 5, 40, 57

• // operator, 5, 40, 57

• /=, //= operators, 7, 41

• : (colon)

• for dictionaries, 18

• for slicing operator, 10, 47–49

• := operator, 8, 12, 39, 54, 57

• = operator, 3, 51

• == operator, 6, 42, 57, 93

• testing for None with, 87

• [] (square brackets), 13

• # comments, 2

• % (percent sign)

• in byte formatting, 253

• in numbers converted to text strings, 251

• operator, 5, 9, 39–40, 57, 298, 310

• %=, &=, ^= operators, 7, 41

• &, ^ operators, 6, 18, 40, 50, 57, 309

• _ (undescore)

• as variable, 2, 17, 46, 61

• in function names, 106

• in names of internal variables, 27

• in numeric literals, 38

• in private attribute and method names, 176

• __ (double undescore)

• in attribute names, 177–179

• in method names, 27, 88

• ~ operator, 6, 40, 57

• \ (backslash), as path separator, 281

• | operator, 6, 18, 40, 50, 57, 302, 309

• |= operator, 7, 41

• >, < operators, 6, 42, 57

• >=, ⇐ operators, 6, 42, 57, 93

• », « operators, 6, 40, 57

• »=, «= operators, 7, 41

• »> prompt, 1

• { } (curly braces), 20

• for dictionaries, 18

• in f-strings, 252

• Python ABC base class, 185

• Python abc module, 185

• Python abs() function, 5, 40, 297

• Python __abs__() method, 91

• Python @abstractmethod decorator, 130, 185

• Python __abstractmethods__ attribute, 222

• Python add() method, 18, 50, 309

• Python __add__() method, 27, 80, 90–91

• Python addition, 5

• Python __aenter__(), __aexit__() methods, 136

• Python __aiter__(), __anext__() methods, 137

• Python all() function, 47, 297

• Python __all__ variable, 229, 240–241

• Python and operator, 6–7, 43, 57, 92

• Python __and__() method, 90

• Python annotations, 23

• Python __annotations__ attribute, 107, 129, 222, 242

• Python any() function, 47, 297

• Python append() method, 13, 26, 300, 307, 313

• Python applicative evaluation order, 101

• Python archives, working with, 284

• Python argparse module, 33, 255

• Python args attribute, 64–65, 70–315

• Python arguments, see Python functions, arguments of

• Python arithmetic operators, 5, 40

• Python ArithmeticError exception, 67–68, 314–318

• Python as qualifier, 31, 64, 75, 99, 226

• Python as_integer_ratio() method, 303

• Python ascii() function, 253, 297

• Python asctime() function, 293

• Python assert statement, 77–78

• Python AssertionError exception, 68, 77, 315

• Python assignment expression operator, see = operator

• Python assignments, 38–39, 41, 83

• Python augmented, 7, 41, 47, 92, 111

• Python async for, Python async with statements, 137

• Python async keyword, 135, 136

• Python asyncio module, 135, 137, 151, 271–274, 285

• Python atexit module, 26

• Python AttributeError exception, 68, 98, 207, 304, 315

• Python attributes, 79, 98

• Python attributes binding, 167, 207–208

• Python attributes deleting, 301

• Python attributes fully qualified, 158

• Python attributes internal, 177–179

• Python attributes lazy evaluation of, 214

• Python attributes no type contraints on, 179

• Python attributes of classes, 308

• Python attributes of functions, 129–130

• Python attributes of objects, 157–158, 304, 310

• Python attributes public, 176

• Python await statement, 135–137, 151

• Python awaitables, 135

banker’s rounding, 5

base classes, 160

abstract, 185–188

invoking menthods of, 313

linking to, 207

__slots__ variable and, 210

tuple of, 222

used for type hinting, 184–185

base64 module, 274

BaseException exception, 67–68, 314

__bases__ attribute, 207, 222

bash shell, 1

bin() function, 37, 297

binary data structures, 288

binary integers, 6

binascii module, 274

bit manipulation, 6

bit_length() method, 305

bitwise operators, 6, 40, 57

blocking, 269–273

BlockingIOError exception, 270, 316

bool class, 297

bool type, 298

__bool__() method, 93–95

Boolean values, 6–7, 38, 43–44, 297

bound methods, 158, 183

break statement, 8, 12, 62–63, 141

breakpoint() function, 298

BrokenPipeError exception, 316

BSD socket interface, 286

BufferedXXX classes, 260

BufferError exception, 315

byte arrays, 247, 266, 298–300

bytearray type, 247, 298

bytes, 247–248

comparing, 43

converting to text, 274

formatting, 253–254

operations on, 298–300

serializing objects into, 268

bytes module, 274

bytes type, 247–248, 298

__bytes__() method, 94–95

BytesIO class, 280

C programming language, 281, 286, 288

__call__() method, 98, 219

callable() function, 301

callback functions, 114, 116

passing arguments to, 118–121

returning results from, 121–123

CallbackError exception, 122

capitalize() method, 298, 310

casefold() method, 310

category() function, 295

__cause__ attribute, 65, 71–73, 315

__ceil__() method, 91

center() method, 298, 310

cgi module, 275

characters

end of file (EOF), 2, 68, 315

line-feed, see newline characters

ordinal values of, 307

check_output() function, 288–289

child classes, see subclasses

ChildProcessError exception, 316

chr() function, 301

circular dependency, 82

class methods, 89, 170–172, 222, 301

class statement, 27, 154–155, 215–218

base-class names in, 160

class variables, 169–172, 222

mutating, 112

__class__ attribute, 206, 223

classes, 80, 153–223

adding methods to, 28

body of, 215

built-in, 313

creating, 160, 215–218

duplicating definitions of, 221

extending, 160

inspecting, 318

internal variables in, 27

linking instances to, 206, 223

membership testing for, 183

names of, 222

namespace of, 215, 218

static methods in, 173

type-checking, 162

uniformity of, 183

user-defined, 179, 206–207

with a single method, 166

classmethod object, 125

@classmethod decorator, 125, 170–171, 183, 197, 213, 301

classobj type, 305

cleanup, 66, 141

clear() method, 300, 302, 309

click module, 255

close() method, 12, 147, 202, 258, 262, 315

closed attribute, 263

__closure__ attribute, 129

closures, 116–117, 129

cls object, 125, 171, 220, 222

code, see also programs

generating, 222, 233

Pythonic, 99–100, 160, 176

readability of, 103, 223

testing, 223

code-checking tools, 87, 107

__code__ attribute, 129–130

collect() function, 82

collections module, 20, 81, 168, 240, 318

comma-separated values (CSVs), 276

command-line options, 15, 33, 254–255, 317, 319

comments, 2

extracting, 55

comparisons, 6, 42, 93

between bytes and text, 248

compile() function, 301

complex() function, 301

__complex__() method, 94–95, 301

compound-interest calculation, 4

compute_usage() function, 282–283

concatenation, 47

of tuples, 16

concurrency, 148, 269, 273, 291–293

conditionals, 4, 7–9, 44–45, 59–60

configparser module, 276

conjugate() method, 303, 305

ConnectionXXXError exceptions, 316

containers, 95–96

__contains__() method, 95–96

context managers, 75–77, 99

asynchronous, 136–137

cleaning up with, 141

__context__ attribute, 65, 72–73, 315

contextlib module, 77, 148

@contextmanager decorator, 148

continue statement, 8, 62–63

control flow

with conditionals, 7–9, 59–60

with exceptions, 64–69, 77

with loops, 60–63

copy() method, 300, 302, 309

copying, of sequences, 47–48

coroutines, 135

generator-based, 146

inspecting, 318

cos() function, 318

count() method, 298, 307, 310, 313

Counter class, 318

cryptographic hash values, 278

csv module, 31, 276

ctime() function, 293

currentframe() function, 132

daemon flag, 291

data encapsulation, 176

data hiding, 178

@dataclass decorator, 134

dataclasses, 196, 233

datetime module, 293, 318

deadlocks, 25, 204

debug variable, 215

debug() function, 133, 281

debugging

breakpoint for, 298

error messages for, 66, 124

exception handling and, 74

in Python development environment, 3

introducing code for, 77–78

logging for, 280

making output for, 162

modules individually, 235

smaller tasks, 145

stack frames and, 133

when using dictionaries, 21

with __dict__ attribute, 211

with repr(), 11

with __repr__(), 28, 196

decode() method, 248, 259, 298, 310

decorators, 104, 124–127, 194–197, 220

deep copies, 83

deepcopy() function, 84

def statement, 22, 27, 101

DEFAULT_BUFFER_SIZE value, 259

defaultdict class, 318

del statement, 19, 50–51, 82–83, 89, 202, 207, 300–302, 307

__del__() method, 89, 201–206

delattr() function, 157, 179, 301

__delattr__() method, 98, 207

delegation, 208–210

__delete__() method, 211

__delitem__() method, 95–96

dependency injection, 165, 176

deque class, 81, 318

descriptors, 211–214, 220, 285

Design Patterns book, 176

detach() method, 261

dict type, 80, 301–302

dict() function, 20, 51, 168

__dict__ attribute, 206–207, 211, 215, 222–223, 242, 302, 313

dictionaries, 18–21

accessing members of, 18

adding unusual items to, 85–87

as literals, 38

assignments on, 83

converting to lists, 20

creating, 18, 20, 53–54

deep vs. shallow copies of, 83

dispatching through, 193

empty, 20, 43

initializing missing items automatically, 318

inserting objects into, 18

iterating over, 21

keys of, 20–21, 294–295

modifying objects of, 18

nested, 19

no ordered comparisons on, 43

number of items in, 306

operations on, 51, 301–302

passed as function parameters, 107

removing elements from, 19, 104

using tuples in, 19

values of, 21

dictionary comprehension, 20, 53–54

dictionary lookups, 176

DictReader class, 277

difference operation, 18, 50, 309

difference() method, 309

difference_update() method, 309

dir() function, 26, 31, 302

__dir__() method, 302

directories, 264

current working, 234

temporary, 289

discard() method, 18, 50, 309

distutils module, 243

division, 5, 303

divmod() function, 5, 40, 303

__divmod__() method, 90

Django library, 279

__doc__ attribute, 106, 129, 222, 242

docopt module, 255

documentation strings, 106, 129, 155, 222, 242

dot operator, see . operator

double-ended queues, 318

duck typing, 167

dump() function, 268

dumps() function, 280

dynamic binding, 167

e, E, in numbers, 37

echo servers, 286

.egg suffix, 234

elif statement, 7–8, 59–60, 193

Ellipsis object, 96

else statement, 7–9, 44–45, 57, 59–60, 63, 66, 193

emails, sending, 285

encode() method, 248, 259, 310

encoding attribute, 13, 259–260, 263

encodings, 248–249, 263

end keyword, 265, 308

endswith() method, 10, 298, 311

__enter__() method, 75, 99, 148

enumerate() function, 61, 303

env command, 256

environment variables, 256

EnvironmentError exception, 314–316

EOF (end of file) character, 2, 68, 315

EOFError exception, 68, 315

epoll() function, 285

__eq__() method, 93–94

errno attribute, 316

errno module, 277–278

errors

handling, 110–111

logging, 66

errors attribute, 259–260, 263

eval() function, 89, 301, 303, 308

Event class, 292

except statement, 24–25, 64–66, 70, 110

narrowness of, 74

Exception exception, 66–69, 314

exceptions, 24–25, 64–75

altering control flow, 67–69

asynchronous, 69

built-in, 67–68, 75, 314–318

catching, 64, 66, 70, 73–74

chained, 70–73, 315

defining new, 69–70, 74

expected vs. unexpected, 72–73

extracting values attached to, 141

handling, 24–25, 73–75, 110–111, 121–122, 277–278

hierarchy of, 67–68, 70

ignoring, 65–66

predefined, 315–318

propagating, 64

raising, 64, 69, 110, 147, 315

standard attributes of, 64–65

traceback messages of, 70, 73

user-defined, 69, 314

wrapping with a function, 54

exec() function, 133–134, 233, 301, 303

__exit__() method, 75, 99, 148

expandtabs() method, 298, 311

expressions, 3, 38–39

evaluating, 43, 303

extend() method, 300, 307

Extensible Markup Language (XML), 295

f-strings, 4, 9, 11, 251–252

False value, 6–7, 38, 43–45, 297–298

fast lookups, 19

fcntl module, 262, 278

fcntl() function, 278

file descriptors, 257, 262

file keyword, 265, 308

file modes, 258, 263

file objects, 258, 262, 307

attributes of, 263

implementing, 279

manipulating, 261

methods supported by, 261

standard, 263

file pointers, 262

__file__ attribute, 36, 242

__file__ variable, 241

FileExistsError exception, 258, 316

FileIO class, 260

filename attribute, 316–317

fileno() method, 262

FileNotFoundError exception, 277, 316

files

converting between binary and text, 261

copying, 284, 319

encoding of, 13, 263

locking, 278

metadata of, 282

names of, 257–258, 263

newline characters in, 260, 263

opening, 12, 256–258

overwritting, 258

parsing, 105

paths to, 281–283

reading, 12–13, 262

removing, 284, 319

state of, 263

temporary, 289

writing to, 262, 268

filter() function, 128, 303

filtering, 127–128

finally statement, 25, 66, 141

find() method, 10, 299, 311

first-class objects, 85–87, 115, 242

flag variables, 63

flask library, 279

float() function, 11, 303, 315

__float__() method, 94–95, 303

FloatingPointError exception, 67, 314–315

floats, 3, 5, 37–38, 303, 315

converting to text, 250–251

precision of, 288

rounding, 5, 308

flock() function, 278

__floor__() method, 91

__floordiv__() method, 90

flush() method, 259, 262

flyweight pattern, 176

for statement, 12–13, 21–22, 45, 60–63, 140, 176

for reading lines in a file, 262

implementing, 97

nested, 144–145

on lists, 52

format() function, 11, 94, 250, 304

format() method, 9, 252–253, 311

__format__() method, 94, 304

format_map() method, 311

from statement, 31, 228–230, 237, 316

from_ prefix, in method names, 172

from_bytes() method, 305

fromhex() method, 274, 303

fromkeys() method, 302

frozenset() function, 304, 309

__fspath__() method, 257

function call operator, 56

functions, 22–24, 101–131, 137

accepting iterables, 47

arguments of

default, 23, 101–102, 115

default values for, 87, 157

evaluated left-to-right, 101

keyword, 103–104

number of, 101–102

order of, 101

positional, 105–106

asynchronous, 135–137, 272, 317

attribute access, 207

attributes of, 129–130

built-in, 297–314

callback, 114, 116, 118–123

comparing, 131

debugging messages in, 124

defining, 22, 101

delayed execution of, 145

documenting, 106, 129, 155

emulating, 98

evaluating, 116

helper, 106

higher-order, 115–118

inspecting, 131–133, 318

invoking, 22, 101, 111

local variables in, 24, 107, 111–113, 149–151

metadata of, 124–125, 130

naming, 106, 129

nested, 113, 116–117, 129

recursive, 114

return values of, 23, 109–110

side effects in, 108

signature of, 130–131

type hints in, 107, 129, 155

wrappers around, 124

functools module, 94

futures, 123

garbage collection, 26, 81–83, 89, 141, 203–204

gc module, 82

__ge__() method, 93

generator expressions, 54–56, 128

GeneratorExit exception, 147, 314–315

generators, 97, 139–152

asynchronous, 317

creating, 54

delegating, 142–144

emitting I/O streams, 265–266

enhanced, 146–151, 266–267

for repeated iterations, 142

inspecting, 318

terminating, 315

get() method, 19, 302

__get__() method, 211–213

get_data() function, 242

getattr() function, 157, 179, 193–194, 304

__getattr__() method, 98, 207–211

__getattribute__() method, 98, 207, 211

__getitem__() method, 95–96, 159–308

getsize() function, 282

__getstate__() method, 268

glob() function, 264

global statement, 112

globals() function, 131, 303–304

__globals__ attribute, 129, 131

globbing, 264

gmtime() function, 293

__gt__() method, 93

hasattr() function, 157, 179, 304

hash() function, 304

__hash__() method, 93–94

hashlib module, 278

help() command, 22

hex() function, 37, 95, 304

hex() method, 274, 299, 303

higher-order functions, 115–118

http package, 279

httpx library, 279, 294

HyperText Markup Language (HTML), 279

Hypertext Transfer Protocol (HTTP), 279, 293–294

__iadd__(), __iand__() methods, 91–92

id() function, 80, 304

identifiers, 38

identity checks, 92

__idivmod__() method, 91–92

if statement, 7–9, 39, 44–45, 52, 57, 59–60, 193

__ifloordiv__(), __ilshift__(), __imatmul__(), __imod__() methods, 91–92

import statement, 15, 30–35, 59, 225–237, 241, 245, 316

inside a function, 228, 231

ImportError exception, 31, 67–68, 226, 237, 316

importlib library, 232

__imul__() method, 91–92

in operator, 19, 45, 50–52, 57, 96, 302

in-place assignment, see assignments, augmented

indent() function, 290

indentation, 4, 316

IndentationError exception, 316

index() method, 299, 307, 311, 313

__index__() method, 94–95

IndexError exception, 48, 49, 67, 314, 316

indexing operator, 13

on dictionaries, 18

on tuples, 16

info() function, 281

inheritance, 28–30, 160–163

breaking code with, 162

from built-in types, 167–169

multiple, 163, 187–192, 211

cooperative, 190–192

propagating metaclasses via, 220

__slots__ variable and, 210

supervised, 197–199

via composition, 164–166

via functions, 166–167

via implementation, 163–164

INI files, 276

__init__() method, 27, 70, 89, 134, 154–155, 161, 181–201, 219–220

__init__.py file, 34–35, 235–237, 239–241

__init_subclass__() method, 197–199, 220–222

input() function, 13, 33, 304, 315

input/output (I/O), 247–296

buffering, 258–260

consuming input, 266–267

error handling, 249, 256, 259, 316

generating output, 265–266

handling, 288, 291

in binary mode, 257–259

in text mode, 258–260

nonblocking, 270

polling channels of, 271, 273, 284

insert() method, 13, 26, 300, 307

inspect module, 318

instances, 79, 154–156

adding attributes to, 161, 206

alternate constructors of, 170–172

caching, 200–201, 204–206

creating, 89, 199

deleting an attribute of, 156

destroying, 89, 201

getting, 156

initializing, 89

linking to classes, 206, 223

setting, 156

state associated with, 206, 223

storing data of, 210–211

int class, 80

int() function, 11, 95, 305

__int__() method, 94–95

integers, 3, 305

as literals, 37

base of, 37

binary, 6

converting

to text, 251

to/from bytes, 305

creating strings from

binary, 37, 297

hexadecimal, 37, 299, 303–304

octal, 37, 307

iterating over, 21

precision of, 316

ranges of, 21–22, 308

testing values of, 303

interfaces, 184–188

interpreter, 1, 3

InterruptedError exception, 316

intersection operation, 18, 50, 309

intersection() method, 309

__invert__() method, 91

io module, 260–261, 279–280

ioctl() function, 278

IOError exception, 316

__ior__(), __ipow__() methods, 91–92

ipython shell, 2

__irshift__() method, 91–92 “is a” relationship, 163

is not operator, 42, 57, 80

is operator, 42, 57, 80, 92

is_integer() method, 303

IsADirectoryError exception, 316

isalnum(), isalpha() methods, 299, 311

isascii() method, 311

isatty() method, 262

isdecimal() method, 311

isdigit() method, 299, 311

isdir() function, 282

isdisjoint() method, 309

isfile() function, 282

isidentifier() method, 311

isinstance() function, 64, 81, 183, 305

islower() method, 299, 311

isnumeric(), isprintable() methods, 311

isspace() method, 299, 311

issubclass() function, 184, 305

issubset(), issuperset() methods, 309

istitle() method, 299, 311

__isub__() method, 91–92

isupper() method, 299, 311

items() method, 21, 51, 302

iter() function, 305

__iter__() method, 97–98, 142, 152, 160, 305

iterations, 21–22, 45–47, 60–62, 97–98, 305

ending, 69

handling, 307, 318

nested, 143

producing values for, 139

repeated, 142

reversed, 308

iterator objects

asynchronous, 136–137

creating, 22, 61

implementing, 98, 152

internal stack of, 146

reversed, 97

itertools module, 318

__itruediv__() method, 91–92

__ixor__() method, 91–92

join() function, 281

join() method, 299, 311

JSON format, 280

json module, 280

KeyboardInterrupt exception, 67, 69, 314, 316

KeyError exception, 67, 314, 316

keys() method, 20, 51, 302

kqueue() function, 285

lambda expression, 114–115, 117–118

late binding, 115

lazy evaluation, 116, 214

__le__() method, 93

left-fold operations, 128

len() function, 10, 47, 50, 51, 159, 298, 302, 306, 309–310, 313

__len__() method, 28, 93, 95, 159–160, 308

libraries, 235

line endings, see newline characters

lineno attribute, 317

list class, 14, 80

list comprehension, 17, 52, 55

filtering with, 127

list() function, 20, 47, 55, 81, 168, 306

listdir() function, 264

lists, 13–15

adding items to, 13, 307

as literals, 38, 46

as sequences, 47

assignments on, 83

comparing, 42

concatenating, 14

converting to, from data, 14

creating, 13

deep vs. shallow copies of, 83, 306

defining subtypes of, 81

empty, 14, 43–44, 306

iterating over, 13, 21

modifying, 49–50

nested, 14, 145–146

number of items in, 306–307

passed as function parameters, 107

processing, 52–53, 307

removing items from, 307

slicing, 14

sorting, 307, 310

literals, 37–38

ljust() method, 299, 311

load() function, 268

loads() function, 280

locals() function, 131, 303, 307

localtime() function, 293

Lock class, 291

locks, 25

Logger instance, 280–281

logging module, 254, 280–281

logical operators, 6–7, 43, 57, 92

LookupError exception, 67–68, 314, 316

loops, 4, 7–9, 21–22, 60–63

aborting, 141

flag variables in, 63

numerical indices in, 61

skipping the reminder of, 8, 62

taking items from different sequences, 62

loose coupling, 167

lower() method, 10, 299, 311

__lshift__() method, 90

lstrip() method, 299, 311

__lt__() method, 93–94

main() function, 33, 281

__main__ module, 234

__main__.py file, 235, 239, 245

maketrans() method, 299, 311

map() function, 128, 307

mappings, 18–19, 128, 307

opeations on, 51–52

math module, 318

mathematical operations, 5, 40, 90–92

__matmul__() method, 90

max() function, 47, 94, 128, 307

MD5 algorithm, 278

memory

allocating, 82

reducing usage of, 55, 210–211

MemoryError exception, 68, 316

metaclass keyword, 218–219

metaclasses, 217–222

Method Resolution Order (MRO, 190–192, 222

methods, 79, 154

abstract, 185, 222

available on an object, 26

bound, 158, 183

decorating automatically, 222

defining, 215

fully qualified, 158

implementing, 213

internal, 176

internal variables in, 27

invoking, 154

magic (special), 154, 210

naming, 172, 176

public, 176

redefining, 28, 160

rewriting, 195

static, 173–176, 310

user-defined, 180

Microsoft Excel, 276

min() function, 47, 94, 128, 307

mixin classes, 188–192, 220

__mod__() method, 90

mode attribute, 263

module objects, 226

__module__ attribute, 129, 222

__module__ variable, 215

ModuleNotFoundError exception, 316

modules, 30–32, 225–235

as first-class objects, 242–243

caching, 227–228, 231–233

compiling, 233

debugging, 235

importing, 31, 225–227, 232–234

circular, 230–232

specific definitions from, 228–230

listing contents of, 31

locating, 226

names of, 222, 226, 234, 242

namespaces of, 242, 304

organizing, 33

reloading and unloading, 232–233

renaming, 227

standard library, 31, 273–296, 318–319

third-party, 32

modulo, 5, 307

monads, 123

__mro__ attribute, 190, 207, 222

__mul__() method, 88, 90

multiplication, 5

name attribute, 263

name mangling, 177–179

__name__ attribute, 106, 129, 222, 242

__name__ variable, 33, 234

named fields, 19

namedtuple() function, 134

NameError exception, 68, 111, 316–317

namespace packages, 237

namespaces, 31, 158, 226, 242

global, 112

local, 111

of classes, 215, 218

of packages, 239–240

nc program, 274, 286

__ne__() method, 93

__neg__() method, 91

network programs, 286, 288, 291

__new__() method, 89, 199–201, 219

new_class() function, 216–217

newline attribute, 260

newline characters, 260, 263, 301, 304

controlling, in output, 265

in input, 266

newlines attribute, 263

next() function, 139–141, 307

next() method, 317

__next__() method, 97, 140, 152

None value, 6, 43–44, 87, 102, 108–110

normalize() function, 295

not in operator, 45, 57

not operator, 6–7, 43, 57, 92

NotADirectoryError exception, 316

NotImplemented object, 91, 93

NotImplementedError exception, 68, 93, 316

numbers

comparing, 42

complex, 301, 303, 305

converting

from objects, 94–95

from strings, 11

to text, 250–251

floating-point, 5, 37–38, 250–251, 288, 303, 308, 315

nonempty, 43

precision of, 251

random, 319

sum of, 312

numpy package, 50, 88, 96, 263

object class, 190, 307

inheriting from, 160, 191

objects, 26–30, 79–99, 153

attributes of, 56

built-in, 222–223

checking against classes, 183

comparing, 42, 80, 92–94

converting to built-in types, 94–95

coroutine, 135

deep vs. shallow copies of, 83

first-class, 85–87, 115

hash values of, 93–94, 304

identity of, 80, 304

immutable, 102

implementing operators for, 79

initializing, 27

invoked likes functions, 98

iterable, 45

listing available methods of, 26

location of, 38–39

management of, 89–90

methods available on, 26

mutable, 41, 83–84, 107–108

reference count of, 81–83

references to, 83–84

representations of, 84–85, 297, 308

serialization of, 268–269

sorting, 94

state of, 154

types of, 79, 154

unpacking values of, 45–46, 60

values of, 79, 84–85

oct() function, 37, 95, 307

offset attribute, 317

open() function, 12, 15, 241, 256–261, 279, 307

operating-system functions, 281, 316, 319

operators, 39–40

arithmetic, 5, 40

augmented, 7, 41, 47, 92, 111

bitwise, 6, 40, 57

comparison, 6, 42–43, 93

implementing, 79

logical, 6–7, 43, 57, 92

precedence rules for, 56–58

or operator, 6–7, 43, 57, 92

__or__() method, 90

ord() function, 307

os module, 258, 281, 319

os._exit() method, 317

os.chdir(), os.getcwd() methods, 257

os.environ variable, 256

os.path module, 281–282

os.system() function, 284

OSError exception, 64–65, 67–68, 277, 314, 316–318

output, see input/output (I/O)

OverflowError exception, 67, 314, 316

__package__ attribute, 242

packages, 33–34, 235–242

data files of, 241–242

deploying, 243–244

exporting, 240–241

importing files within, 34

imports within, 237

installing, 36, 244

locating, 36

namespaces of, 239–240

naming, 243

submodules of, running as scripts, 238–239

third-party, 50

pandas library, 277

parameters, see functions, arguments of

parent classes, see base classes

partial() function, 98

partition() method, 299, 311

pass statement, 7, 60, 65

Path class, 282

path separators, 281

__path__ attribute, 242

pathlib module, 257, 264, 281–283

patterns, 176

performance, 55

exception handling and, 111

local variables and, 149–151

optimizing, 210, 220–221

type checks and, 81

PermissionError exception, 277, 316

pickle module, 268–269

pip command, 35–36, 244

poll() function, 285

pop() method, 27, 104, 300, 302, 307, 309

Popen class, 289

popitem() method, 302

__pos__() method, 91

POSIX standard, 281

pow() function, 5, 40, 307

__pow__() method, 90

power, in math, 5, 307

__prepare__() method, 219

primitive types, 3

print() function, 4, 11–13, 84, 265, 308

ProcessLookupError exception, 316

programs, see also code

creating, 2–3

executing, 1, 3, 234–235

loading, 228, 233

side effects in, 108

specifying interpreter in, 3

starting from packages, 244

structuring, 34–35, 59, 235

terminating, 26, 69

properties, 180–183

functions associated with, 207, 211

implementing, 211

@property decorator, 180–182, 308

protocols, 87–99

proxies, 104, 208

push() method, 27

.py suffix, 2, 3, 30, 226, 233

__pycache__ directory, 233

pytest library, 319

Python

applying design patterns to, 176

flexibility of, 86

indentation in, 4, 316

interactive mode of, 1–2

no internal variables in, 27

optimized mode of, 77

package index of, 243

runtime environment of, 254, 319

python shell, 1

PYTHONPATH environment variable, 234

__qualname__ attribute, 129, 222

__qualname__ variable, 215

Queue class, 292

quit(), in REPL, 2

__radd__() method, 90–91

raise statement, 25, 64, 69

__rand__() method, 91

random module, 319

range() function, 21–22, 308

raw_input() function, 315

__rdivmod__() method, 90

re module, 283–284, 319

read() function, 258

read() method, 12, 262, 315

read-evaluation-print loop (REPL), 1

readable() method, 262

readinto() method, 262–263

readline() method, 262, 315

readlines() method, 262

recursion, 114

limit of, 114, 143, 317

RecursionError exception, 317

reduce() function, 128

reference counting, 81–83, 201

reference cycle, 203

ReferenceError exception, 317

registries, 194, 197, 222

regular expressions, 283–284, 319

reload() function, 232

remote servers, 208

remove() method, 18, 50, 300, 307, 309

removeprefix() method, 299, 312

removesuffix() method, 299, 312

replace() method, 10, 299, 312

repr() function, 11, 85, 89, 252, 308

__repr__() method, 28, 89–90, 154–155, 159–199

default implementation of, 160

requests library, 279, 294

resources, controlling, 99

return statement, 59, 109, 135, 140

reverse() method, 300, 307

reversed() function, 97, 308

__reversed__() method, 97, 308

rfind() method, 299, 312

__rfloordiv__() method, 90

rglob() function, 264

rindex(), rjust() methods, 299, 312

__rlshift__() method, 91

__rmatmul__(), __rmod__(), __rmul__()

methods, 90

__ror__(), __round__() methods, 91

round() function, 5, 40, 308

rpartition(), rsplit() methods, 299, 312

__rpow__() method, 90

__rrshift__() method, 91

__rshift__() method, 90

rstrip() method, 300, 312

__rsub__(), __rtruediv__() methods, 90

run() function, 135, 270–271

RuntimeError exception, 68, 114, 316–317

__rxor__() method, 91

sandbox, 36

scripts, 32–33

seek(), seekable() methods, 262

select module, 271, 284–285

select() function, 285

selectors module, 271, 285

self object, 27, 154, 158, 169, 220

send() method, 152

sep keyword, 265, 308

sequences

comparing, 43

mutable, 49–50

operations on, 47–50

set comprehension, 17, 53

set() function, 17–18, 20, 47, 309

__set__() method, 211

__set_name__() method, 212

setattr() function, 157, 179, 310

__setattr__() method, 98, 207, 211

setdefault() method, 302

__setitem__() method, 95–96, 167

sets, 17–18

adding/removing items to/from, 50, 309

as literals, 38, 46

creating, 17, 309

empty, 18

immutable, 304

number of items in, 50, 306, 309

order of elements in, 17

processing, 50–51, 53–54, 309

__setstate__() method, 268

setup() function, 244

setup.py file, 244

setuptools module, 234, 243–244

SHA-1 algorithm, 278

shallow copies, 83

shell, 1, 284, 319

short-circuit evaluation, 43

shutil module, 284, 319

side effects, 108

SIGINT signal, 69

signal module, 69

signature() function, 130–131

__signature__ attribute, 131

Simple Mail Transfer Protocol (SMTP), 285

sin() function, 318

singletons, 176, 200

site-packages directory, 35, 244

sleep() function, 293

slice instance, 96

slice() function, 310

slicing operator, 10, 47–49, 298, 307, 310, 313

implementing, 96

on lists, 14

on tuples, 16

__slots__ variable, 210–211, 220–221, 223

smtplib module, 285–286

socket module, 286–287

sort() method, 108, 307

sorted() function, 47, 114, 310

splatting, 46

split() function, 281

split() method, 10, 300, 312

splitlines() method, 300, 312

sprintf() function (C), 253

sqrt() function, 38, 318

stack frames, 132–133

stack traceback objects, 65, 73

standard error, 263

standard input/output, 263, 304

start keyword, 62

startswith() method, 10, 300, 312

state machines, 176

statements, 59

executing, 303

@staticmethod decorator, 125, 173, 183, 213, 310

statistics module, 47, 319

stdin, stdout attributes, 289

StopAsyncIteration exception, 317

StopIteration exception, 67, 69, 97, 140–141, 147, 307, 317

str() function, 11, 84, 94, 168, 248, 251–252, 310

__str__() method, 94, 171, 310

default implementation of, 160

strategy pattern, 176

strerror attribute, 316

stride argument, 48, 49, 96

StringIO class, 279

strings, 3, 9–12

as literals, 38

as sequences, 47

checking characters of, 311

comparing, 43

concatenating, 10–11, 310

converting

from non-string values, 11, 304

from objects, 94

to numbers, 11

converting to upper/lowercase, 310–312

creating, 11, 310

encoding/decoding, 310

formatting, 9, 11, 250–253, 310–311

iterating over, 21

methods for, 10

nonempty, 43

number of items in, 10, 306, 310

processing, 310–312

representations of, 89–90

substrings of, 10, 310–312

triple-quoted, 9, 38

whitespace in, 312

strip() method, 10, 300, 312

struct module, 288

struct_time object, 293

__sub__() method, 90

subclasses, 81, 160

checking classes against, 184, 305

implementing interfaces, 185

subprocess module, 256, 288–289

subtraction, 5

subtypes, see subclasses

sum() function, 15, 47, 128, 312

super() function, 161, 189–192, 199, 207, 313

superclasses, see base classes

swapcase() method, 300, 312

symmetric difference operation, 18, 50, 309

symmetric_difference() method, 309

symmetric_difference_update() method, 309

SyntaxError exception, 316, 317

sys module, 15, 319

sys.argv list, 33, 254–255

sys.exit() function, 317

sys.getdefaultencoding() method, 259

sys.getfilesystemencoding() function, 257, 264

sys._getframe() function, 132

sys.getrecursionlimit() function, 114

sys.getrefcount() function, 82

sys.modules variable, 227, 232

sys.path variable, 31, 35, 226, 234, 244

sys.setrecursionlimit() function, 114

sys.stderr object, 69, 263–264

sys.stdin, sys.stdout objects, 263–264

SystemError exception, 317

SystemExit exception, 15, 26, 67, 69, 314, 317

TabError exception, 317

tabulation, 19, 311, 318

teletypewriter (TTY), 281

tell() method, 262

telnet program, 274, 286

tempfile module, 289–290

testing

smaller tasks, 145

using file objects for, 279

text, 247–248

converting from binary data, 274

encoding/decoding, 13, 248–250, 255, 259

fitting to terminal width, 290

handling lines of, 260, 263

text attribute, 317

TextIOWrapper class, 260

textwrap module, 290

threading module, 271, 291–293

threads, 271–272

throw() method, 147, 152

time module, 293, 319

time() function, 293

time, handling, 293, 318–319

TimeoutError exception, 316

title() method, 300, 312

to_bytes() method, 305

@trace decorator, 125–126

traceback messages, 24, 315

traceback module, 73

__traceback__ attribute, 65, 73, 315

translate() method, 299–300, 312

True value, 6–7, 38, 43–45, 297–298

__truediv__() method, 90

__trunc__() method, 91

truncate() method, 262

truncating division, 5

try statement, 24–25, 64, 66, 110, 141

tuple type, 313

tuple() function, 47

tuples, 15–17

as keys, 52

as literals, 38, 46

as sequences, 47

comparing, 42

concatenating, 16

creating, 15

empty, 43, 313

indexing, 16

iterating over, 17, 21

named, 109–110

number of items in, 306, 313

returning values from functions with, 23, 109

slicing, 16

unpacking, 16

using in dictionaries, 19

turtle module, 319

type class, 218–220, 313

type hints, 107, 129, 155, 179–180, 222

creating methods from, 197

module-level, 242

with base classes, 184–185

type() function, 70, 80, 154, 217, 313

type-based dispatch, 193–194

TypeError exception, 43, 68, 95, 101, 103, 122, 191, 211, 305, 317

types, 79, 313

built-in, 167–169

checking values against, 81, 305

conversions between, 94–95

types module, 313

UDP servers, 287

unary minus/plus, 5

UnboundLocalError exception, 68, 111, 317

Unicode encoding

code-point values in, 307

in source code, 2

operations on text strings in, 294–295

unicodedata module, 294–295

UnicodeError exception, 67–68, 249, 317

UnicodeXXXError exceptions, 317

union operation, 18, 50, 309

union() method, 309

unittest module, 319

universal newline mode, 260

UNIX

EOF character on, 2

executing files on, 3

low-level I/O control operations on, 278

newline characters on, 260

path separators on, 281

unpack() function, 288

update() method, 18, 168, 302

upper() method, 10, 300, 312

urlencode(), urlopen(), urlparse() functions, 293–294

urllib package, 293–294

urllib.parse package, 294

UserDict, UserList, UserString classes, 168

UTF-8 encoding, 2, 13, 249–250

ValueError exception, 25, 67–68, 317

values, 3, 79

checking against types, 81, 305

minimum/maximum, 307

printing, 265, 308

reducing, 128

representing, 84–85

updating in place, 41

values() method, 21, 51, 302

variables, 3

associated types of, 3, 167

free, 114–115

global, 111–113

local, 24, 111–113, 134, 149–151

names of, 3

reassigning, 108

starred, 46

type hints for, 107

unbound, 317

vars() function, 313

venv command, 36

virtual environment, 36

walrus operator, see := operator

warning() function, 281

weak references, 204–206, 317

weakref module, 204, 317

__weakref__ attribute, 206

web servers, 279

websites, 275, 294

while statement, 4, 7–9, 12, 39, 60–62

Windows

EOF character on, 2

executing files on, 3

failed system calls on, 318

newline characters on, 260

path separators on, 281

WindowsError exception, 318

with statement, 12, 25, 75–77, 99, 202, 256, 289–290

wrap() function, 290

wrappers, 104, 208

@wraps decorator, 124–125

writable() method, 262

write() function, 265

write() method, 13, 262

write_through attribute, 263

writelines() method, 262

xml package, 295–296

xml.etree package, 295

__xor__() method, 90

yield from statement, 142–143

yield statement, 97, 139–142, 265

used as an expression, 146–147

ZeroDivisionError exception, 67, 314, 318

zfill() method, 300, 312

zip() function, 62, 314

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