Python Study (8) – Function

Introduction

Function is a Python’s basic structure. Function often is used to reuse code. you can repeat task that define a function for code reuse.

Function Advantage 

(1) Maximizing code reuse and minimizing redundancy
     In developing software,  don't repeat yourself is a a principle . We use function to achieve the goal in Python.A section code is adopted many times or offer other to use. We need to package to a function and offer many time for reuse .

(2) Procedural decomposition
A flow program is combined from


Function component 

(1) def

• Syntax

def name(arg1, arg2….) :     statements …

• Example

def add(a, b):            print(a+b) >>>add(1,2) 3

(2) return

• Syntax

def name(arg1, arg2….) :     statements … return result

• Example

def add(a, b): return a+b >>>print(add(1,2)) 3

(3) lambda
     lambda is keyword in python, It mainly is used to create anonymous function.

• Syntax

lambda arg1, arg2, ....: statments # lambda is equal to follow as :

def fun(arg1, arg2,….) :    return result

• Example

>>> add = lambda a, b : a+b >>> add <function <lambda> at 0x0000000003327D08> >>> add(1,2) 3

(3)lambda

Variable Scope 

>>> k=1 >>> def add(a,b):     k=10     print(k) >>>k 1 >>>add(1,2) 10

Why k value is different in add function and outside add function ? 
1.Local variable : In a function , A variable is declared  and the variable only use in function
2. nested variable: In nested functions, A variable is declared in enclosing function.
3. global variable : A variable is declared  and the variable is hold  in file
4. nonlocal variable: In Python3.x  it introduce a new nonlocal statment , It only define in a function.

Example

>>> counter = 1 >>> def increament():          global counter          counter = 10          counter = counter +1          print(counter) >>> increament() 11 >>> counter 11

 

 

Build-in Scope :
    Servial variable is builed-in python’s library.

>>> import builtins >>> dir(builtins) ['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException', 'BlockingIOError', 'BrokenPipeError', 'BufferError', 'BytesWarning', 'ord', 'pow', 'print', 'property', 'quit', 'range', 'repr', 'reversed', 'round', 'set', 'setattr', 'slice', 'sorted', 'staticmethod', 'str', 'sum', 'super', 'tuple', 'type', 'vars', 'zip']