Python-基础(4)-Functions

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Python Functions

Lambda

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>>> fn = lambda x: x**3
>>> fn(2)
8

>>> (lambda x: x**3)(2)
8

>>> (lambda x: [x * _ for _ in range(10)])(3)
[0, 3, 6, 9, 12, 15, 18, 21, 24, 27]

Declare Function

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def fn_name(): ## Where fn_name represents the function name
    ........
    ........

Get Function Name

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## First Declare a function 
def fn_name():
    .......
    .......


>>> fn_name.__name__
'fn_name'

Document a Function

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## Document a function with three single quotes
def check():
    '''This function is documented'''
    return


>>> check.__doc__
'This function is documented'

Arguments

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>>> def multiply(a, b=0): ## b is 0 by default
...     return a * b
...
>>> multiply(1, 3) ## 3 * 1
3
>>> multiply(5) ## 5 * 0
0
>>> multiply(5, b=3) ## 5 * 3
15

Generator

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def count(start, step):
    while True:
        yield start
        start += step

>>> counter = count(10, 5)
>>> next(counter)
(15)

>>> next(counter) ## Increments by 5 from the previous result
(20)

>>> next(counter)
(25)

>>> next(counter), next(counter), next(counter)
(30, 35, 40)

Decorator

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>>> from functools import wraps

>>> def decorator_func(func):
...     @wraps(func)
...     def wrapper(*args, **kwargs):
...         print("Before calling {}.".format(func.__name__))
...         ret = func(*args, **kwargs)
...         print("After calling {}.".format(func.__name__))
...         return ret
...     return wrapper
...
>>> @decorator_func
... def check():
...     print("Inside check function.")
...
>>> check()
Before calling check.
Inside check function.
After calling check.