Python function (i)

Define a function

• The first line of the function statement can optionally use the document string-for storing the function description.
• The function contents begin with a colon and are indented.
• return [expression] ends the function, optionally returning a value to the caller. Return without an expression is equivalent to returning None.

def printme():"Print incoming string to standard display device"printreturn

Printme("I want to invoke the user custom Function");  

Parameter passing

In Python, a type belongs to an object, and a variable is of no type:

A=[1,2,3]a="Runoob"        

In the above code, [All-in-one] is a list type,"Runoob" is a String type, and the variable A is no type, she is simply a reference to an object (a pointer), either a list type object, or a point to Stri Ng type Object.

Can change (mutable) and non-changing (immutable) objects

In Python, strings, tuples, and numbers are objects that cannot be changed, and List,dict are objects that can be modified.

• immutable Type: variable assignment a=5 and then assign value a=10, here is actually reborn into an int value object 10, then a point to it, and 5 is discarded, not change the value of a, the equivalent of a new student into a.

• Variable type: variable assignment la=[1,2,3,4] after assigning a value la[2]=5 is to change the value of the third element of List LA, itself LA is not moving, but its internal part of the value has been modified.

Parameter passing of the Python function:

• immutable types: values such as C + + are passed, such as integers, strings, and tuples. such as fun (a), passing only a value, does not affect the A object itself. For example, in Fun (a) to modify the value of a, just modify another copy of the object, does not affect the a itself.

• mutable types: references such as C + + are passed, such as lists, dictionaries. such as Fun (LA), is the real transfer of LA, the modified fun outside of LA will also be affected

Everything in Python is an object, strictly meaning we can't say value passing or reference passing, we should say immutable objects and pass mutable objects.

Python-Pass Immutable object instance

#!/usr/bin/python#-*-coding:utf-8-*-defchangeint():=Ten=2  Changeint(b)print# result is 2          

Passing a Mutable object instance

Python function (i)