The first day of Python

Install Python

First, Windows
1. Download the installation package:

https://www.python.org/downloads/

2. Installation directory:

Python installed in the C \ Directory

3. Configure Environment variables:

"Right-click Computer" – "Properties" – "Advanced system Settings" – "Advanced" – "Environment Variables" – "In the Second content box, locate a row with the variable named path, double-click the" –> "Python installation directory to append to the variable value, and split"

Second, Linux

PYTHON-V Check Version

1, install GCC, for compiling;

2, download the source package, https://www.python.org/ftp/python/;

3, decompression and access to source files;

4. Compile and install

./configuremake allmake install

5. View version
/usr/local/bin/python2.7-v
6. Modify the default Python version
mv/usr/bin/python/usr/bin/python2.6
Ln-s/usr/local/bin/python2.7/usr/bin/python
7. To prevent Yum from performing exceptions, modify the Python version used by Yum
Vi/usr/bin/yum
Change the head #!/usr/bin/python to #!/usr/bin/python2.6

Third, Python's first code

Create a hello.py file

Print (' Hello world ')

Execute Python hello.py to

Iv. Explanatory device

The role of the interpreter: explicitly stating that the hello.py script is executed by the Python interpreter;

#!/usr/bin/env python

--Coding:utf8- -<--– function is to specify the character set, can support Chinese display (there is a strict distinction on the python2, Python3 not)

Print (' Hello world ')

V. Notes

When the line stares: # is annotated content
Multiline Comment: "" "Annotated Content" ""

Vi. Execute script incoming parameters

Python has a large number of modules, which makes developing Python programs very concise. The class library includes three:

Python-supplied modules
Industry-Open Source modules
Modules developed by programmers themselves
Python internally provides a SYS module where SYS.ARGV is used to capture parameters passed in when executing a python script

#!/usr/bin/env python
#--Coding:utf8--

Import Sys

Print (SYS.ARGV)

Vii.. pyc file

When you execute Python code, if you import a different. py file, a. pyc file with the same name is automatically generated during execution, which is the bytecode generated after the Python interpreter was compiled.
PS: Code is compiled to generate bytecode, and bytecode can be obtained by decompile.

Viii. variables

1. Defining variables

#!/usr/bin/env python

#--Coding:utf-8--

Name = "Xiaobai"
The code above declares a variable named: Name, and the value of the variable name is: "Xiaobai"
Rules for variable definitions:

Variable names can only be any combination of letters, numbers, or underscores
The first character of a variable name cannot be a number
The following keywords cannot be declared as variable names
[' and ', ' as ', ' assert ', ' Break ', ' class ', ' Continue ', ' Def ', ' del ', ' elif ', ' Else ', ' except ', ' exec ', ' finally ', ' for ', ' F ' Rom ', ' Global ', ' if ', ' import ', ' in ', ' was ', ' lambda ', ' not ', ' or ', ' pass ', ' print ', ' raise ', ' return ', ' try ', ' while ', ' WI Th ', ' yield ']

Nine, enter input

#!/usr/bin/env python

#--Coding:utf-8--

Name = input (' Please enter your name: ')

Print (name) output variable name

When entering a password, if you want to be invisible, you need to take advantage of the Getpass method in the Getpass module, namely:

#!/usr/bin/env python

#--Coding:utf-8--

Import Getpass

#将用户输入的内容赋值给 the name variable

PWD = Getpass.getpass ("Please enter password:")

Print (PWD)

Ten, Process Control

Requirement One: Login verification password

#!/usr/bin/env python

#--Coding:utf-8--

#提示输入用户名

#提示输入密码

#判断用户名与密码是否正确 if the correct output login successful welcome xxx if failed output login failed, please re-login

Import Getpass

Name = input (' Please enter user name: ')

PWD = input (' Please enter password: ')

If name = = "Root" and pwd = = "123":

Print (' login successful, welcome root ')

Else

Print (' Login failed, please re-login ')

Requirement Two: Export its permissions according to user input content

#根据用户输入内容打印其权限

#xiaobai Super Admin

#xiaoqiang General Administrator

#xiaohong

#其他 Ordinary Members

Name = input (' Please enter your name: ')

If name = = Xiaobai:

Print (' Super admin ')

elif name = = Xiaoqiang:

Print (' normal admin ')

elif name = = Xiaohong:

Print (' housing ')

Else

Print (' normal member ')

Add: "=" represents the assignment "= =" For comparison,

Xi. and while Loops

1. Basic cycle

#while conditions:

#如果条件为真, execute the statement;

#如果条件为假, the statement is not executed;

2. Break

Break to exit all loops

While true:

    print (‘python’)    break    print (‘666’)

The above statement only outputs Python, and exits the loop after a break.

3, continue

Continue is used to exit the current loop and continue the next loop

While true:

print (‘python’)continueprint (‘666’)

Output is always output python

Exercises

1. Use while loop input 1 2 3 4 5 6 8 9 10
2. For all numbers of 1-100
3. All odd numbers in output 1-100
4. All even numbers in output 1-100
5, Beg 1-2+3-4+5 ... 99 of all numbers of the and
6. User Login (three chance retry)

The first day of Python