1. Variable of function

Local and global variables:

Any variable in Python has a specific scope

Variables defined in a function can only be used inside the function, and those variables that can only be used in specific parts of the program are called local variables

Variables defined at the top of a file can be called by any function in the file. These variables that can be used by the entire program are called global variables.

def fun():

    x=100

    print x

fun()

x = 100



def fun():

    global x   //statement

    x +=1

    print x

fun()

print x

External variable changed:

x = 100

def fun():

    global x   //statement

    x +=1

    print x

fun()

print x

Internal variables are also available externally:

x = 100

def fun():

    global x

    x +=1

   global y

    y = 1

    print x

fun()

print x

print y

x = 100

def fun():

    x = 1

    y = 1

    print locals()

fun()

print locals()

{'y': 1, 'x': 1}

//Count the variables in the program and return a dictionary

{'__builtins__': <module '__builtin__' (built-in)>, '__file__': 'D:/PycharmProjects/untitled/python/2018.01.03/bianliang.py', '__package__': None, 'x': 100, 'fun': <function fun at 0x02716830>, '__name__': '__main__', '__doc__': None}

2. Return value of function

Function return value:

The function returns a specified value when called

Function call returns None by default

Return return value

The return value can be of any type

When return is executed, the function is terminated

Difference between return and print

def fun():

    print 'hello world'

      return 'ok'

    print 123

print fun()

hello world

123

None



#/usr/bin/env python

# -*- coding:utf-8 -*-

# 2018/11/27 21:06

# FengXiaoqing

#printPID.py

import sys

import os

def isNum(s):

    for i in s:

        if i not  in '0123456789':

	   return False

    return True

for i in os.listdir("/proc"):

    if isNum(i):

	print i



import sys

import os

def isNum(s):

    if s.isdigit():

        return True

    return False

for i in os.listdir("/proc"):

    if isNum(i):

       print i

Or:

#/usr/bin/env python

# -*- coding:utf-8 -*-

# 2018/11/27 21:06

# FengXiaoqing

# :printPID.py

import sys

import os

def isNum(s):

    if s.isdigit():

        return True

    else:

        return False

for i in os.listdir("/proc"):

    if isNum(i):

       print i