What does def mean in python

Functions are similar to encapsulated program fragments. Allows you to give a block of statements a name, allowing you to run it any number of times using the specified name anywhere in your program.

def (the first three letters of define) is a keyword used to declare a function. (Recommended learning: Python video tutorial)

The format of def declaration function is:

def 函数名(参数1，参数2，...，参数n)：
     函数体

For example:

def fib(n):                   
   print 'n =', n            
   if n > 1:                 
       return n * fib(n - 1)    
   else:                     
       print 'end of the line'        
   return 1

The function return value type is not fixed, and there is no need to specify the data type of its return value when declaring a function.

The function can even have no return value. If there is no return value, the system will return the empty value None by default.

Optional parameters: You can specify the default value of the parameter. If no parameter is specified when calling, the default value will be used.

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