1, the definition of the function
Format: DEF <function name> (<parameter (0 or more)>):
<function body>
return <Return value>
2, the function of the optional parameters
When the function definition, optional parameters may be used. When using the optional parameter should be placed behind the non-optional parameters, and then call this function when the optional parameters can not give it a value
such as:
def fact(n,m = 1):
s = 1
for i in range(1,n+1):
s *= i
return s//m
print(fact(10))
print(fact(10,10))
3, the function of the variable parameter
Refers to the total number of functions defined time uncertain parameters: variable parameters
def fact(n,*b):
s = 1
for i in range(1,n + 1):
s *= i
for item in b:
s *= item
return s
print(fact(10,3))
print(fact(10,3,4,5,6))
This is time and b is a combination of a data type
4, transmission parameters
When function calls, passing parameters can be passed in accordance with the location or the name of fashion
def fact(n,m=1):
s = 1
for i in range(1,n + 1):
s *= i
return s//m
fact(10, 5) #按照位置
fact(m=5, n=10)#按照名称
5, the return value of the function
Function can return a value, or may not, can return, may not
return 0 return value can be passed, may be any of a plurality of return value passed
multiple return values directly returns a tuple
def fact(n,m=1):
s = 1
for i in range(1,n + 1):
s *= i
return s//m, n, m
fact(10,5) #这里将会返回一个包含三个元素的元组
a,b,c = fact(10,5)
6, local variables and global variables
Rule 1: function variables are local variables, in order to use a global variable in a function, use global word reserved
n, s = 10, 100
def fact(n):
global s #使用global声明这是一个全局变量
for i in range(1,n + 1):
s *= i
return s
print(fact(n),s)
Rule 2: Create a local variable and not as a combination of data types, the global variable is equivalent to
ls = ['F', 'f']
def func(a):
ls.append(a)
return
func("C")
print(ls)
7, lambda functions
lambda function returns the name of the function as a result of
lambda anonymous function is a function, i.e., without the function name
with lambda reserved words defined, the function returns the name of the result is
the function used to define simply the lambda function can be expressed in a line
using the format: < function name> = lambda <parameter>: <expression>
is equivalent to: DEF <function name> (<parameters>):
<function name>
return <return value>
f = lambda x,y : x + y
f(10,15)
f = lambda : "这是一个lambda函数"
print(f())
Not recommended for regular use
