Functions

Question 1

Arguments

Answer 1

positional, keyword

variable-length (varargs):
*args, **kwargs

actual parameters

Question 2

Parameters

Answer 2

(pos, /, pos_or_kw, *, kw)

required
optional

formal parameters

PEP 570

Question 3

Parameters order

Answer 3

non-default parameters, default parameters

Question 4

Arguments order

Answer 4

positional, keyword

Question 5

Lambda

Answer 5

bound variable
single expression
no type annotations

argument to higher-order function

key function in sort

Question 6

Global Scope

Answer 6

global variable
global keyword
module scope

global variables are available from any scope except built-in

Question 7

Local Scope

Answer 7

declared inside function
available within the function

Question 8

Nonlocal Variable

Answer 8

nonlocal keyword
used in nested functions

defined in an outer (enclosing) scope but not in the global scope

Question 9

Enclosing Scope

Answer 9

scope of outer function

nonlocal scope

Question 10

Built-in Scope

Answer 10

special reserved keywords

__builtins__ module

Question 11

LEGB

Answer 11

Local
Enclosing
Global
Built-in

Question 12

First-Class Function

Answer 12

• assign to variable
• pass as an argument
• return from function

first-class citizen

Python has first-class functions

Question 13

Higher-Order Function

Answer 13

a function that can take other functions as arguments or return functions as results

functions that work on other functions

map, filter

Question 14

Free Variable

Answer 14

variable that is used in a code block but not defined there

in closure defined in enclosing scope

can be nonlocal

can be global if the nearest enclosing scope contains a global statement

Question 15

Closure

Answer 15

function that retains access to variables from the enclosing scope even after the outer function has finished executing

function.__closure__

closure factory

Question 16

Decorator

Answer 16

function/callable that takes a function/callable and returns a function/callable

def decorator(func):
    def wrapper(*args, **kwargs):
        ...
        result = func(*args, **kwargs)
        ...
        return result
    return wrapper

allow to extend and modify behavior of a callable without permanently modifying callable itself

Question 17

Pie-Decorator

Answer 17

@decorator
def func:
    ...

func = decorator(func)

Question 18

Decorator with optional arguments

Answer 18

def name(_func=None, *, key1=value1, key2=value2, ...):
    def decorator_name(func):
        ...
    if _func is None:
        return decorator_name
    else:
        return decorator_name(_func)

Question 19

Top-level code

Answer 19

first user-specified module that starts running

__name__ == ‘__main__’

entry point

Question 20

Decorator with arguments

Answer 20

def name(args):
    def decorator_name(func):
        ...
    return decorator_name

Question 21

Functools Wraps

Answer 21

functools.update_wrapper(wrapper, wrapped, assigned=WRAPPER_ASSIGNMENTS, updated=WRAPPER_UPDATES)

update wrapper function to look like wrapped function

adds __wrapped__ to wrapper that refers to function being wrapped

metadata of original function

@functools.wraps(wrapped, assigned=WRAPPER_ASSIGNMENTS, updated=WRAPPER_UPDATES)

from functools import wraps

def decorator(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        ...

Question 22

__name__

Answer 22

for debugging