python installation and variable settings

python Download: www.python.org

python3: continuing update

python2: continuing update

Environment variable settings:

Computer Properties - Advanced - Environment Variables

Found Path, python installed in the path added to the path, separated by semicolons English format and other content

If a computer several python installation package is installed, when the execution will be run in accordance with the installation time, perform the first installation of python

You can modify the installation directory exe file name to distinguish

Output '' hello world '':

Edit text, write the following code

print('hello world')

Save with cmd execution

Python has nothing to do with the file extension, which can be txt, can be py, that is to say, it can be arbitrary file extensions

File extension appears to be arbitrary, but if when you import the module, if not .py, will be allowed to import, therefore, python file name should be saved as .py

python performed in two ways:

1.python interpreter, enter the file path to execute py

2.python, enter the interpreter, real-time input for execution

In linux code:

#！ /usr/bin/env python
print('hello world')

The first sentence indicates to the system python in linux where, at run time input "./.2.py" will execute python code

In python2, insert coding: utf8

# -*-coding:utf8 -*-
print('hello world')

When print in Chinese, is executed successfully, otherwise it will error

But regardless of the Chinese problem python3

When the code has input, it will wait for user input values in order to enter the following program is executed

# -*- coding:utf8 -*-
n=input('please input your name:')
print(n)

receiving input values for n, n is a variable

Variable names can only consist of letters, numbers, underscores, but the numbers do not begin with

Keywords can not be used as variable names

The variable name is best not to repeat things and built-in python

Conditional statements:

if 条件:
  print（'ok'）
else:
  print('error')

if Condition 1: 
  Results 1 
elif Condition 2: 
  Results 2 
elif Condition 3: 
  Results 3 
the else : 
  Results. 4 

Print ( ' OK ' )

If you do not want to execute the statement after the if condition, use the keyword pass

if the condition:
   Pass 
the else :
   Print ( ' OK ' )

Basic data types:

String: content quotation marks, "***", "***", '' '***' '' '' '***' ""

Addition of the string, the string is connected speaking

Multiplication of the string, the string is repeated many times

Digital: Digital no quotes

There are digital Math

* If there are two, represents power, such as 2 ** 4, 4 th power of 2 represents

% Indicates modulo 39 7% 8 =

// represents a quotient, 8 39 // 4 =

cycle:

Endless loop

while 1==1：
  print（'ok'）

import time
while 1==1:
  print('ok',time.time())

It does not mean a '! = 'Represents

python installation and variable settings

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