- 简单的函数定义如下
# def funcName(arg)
def fib(n): # write Fibonacci series up to n
... """Print a Fibonacci series up to n."""
... a, b = 0, 1
... while a < n:
... print(a, end=' ')
... a, b = b, a+b
... print()
- Default Argument Values
default argument又称为optional argument，可以不传递。其他参数称为required argument，必须传递。
def ask_ok(prompt, retries=4, reminder='Please try again!'):
#可以通过以下方式调用该函数
ask_ok('hello')
ask_ok('hello', 2)
ask_ok('hello', 2, 'world!')
- Keyword Arguments(
kwarg=value)
除了通过上述方式传参，还可以指定参数名称传参。
- key argument必须在positional argument之后调用。
- key argument的顺序不重要
def parrot(voltage, state='a stiff', action='voom', type='Norwegian Blue'):
#可以通过以下方式调用该函数
parrot(1000) #positional argument
parrot(voltage=1000000, action='VOOOOOM') # 2 keyword arguments
#不合法调用，key argument必须在positional argument之后调用
parrot() # required argument missing
parrot(voltage=5.0, 'dead') # non-keyword argument after a keyword argument
parrot(110, voltage=220) # duplicate value for the same argument
parrot(actor='John Cleese') # unknown keyword argument
- Arbitrary Argument Lists
-
*会被wrapped up成一个tuple -
**会被wrapped up成一个dictionary
def cheeseshop(kind, *arguments, **keywords):
print("-- Do you have any", kind, "?")
print("-- I'm sorry, we're all out of", kind)
for arg in arguments:
print(arg)
print("-" * 40)
for kw in keywords:
print(kw, ":", keywords[kw])
- Unpacking Argument Lists
可以通过`*``**`解包list或dictionary传给参数
def parrot(voltage, state='a stiff', action='voom')
>>> d = {"voltage": "four million", "state": "bleedin' demised", "action": "VOOM"}
>>> parrot(**d)
- 查看函数文档
print(my_function.__doc__)
reference
https://docs.python.org/3/tutorial/controlflow.html#defining-functions