Python Development (second article): Initial python

Types of Erpython:

• The official version of Cpython Python, implemented using the C language, is the most widely used, and the Cpython implementation converts the source file () (py file) into a bytecode file (PYc file) and then runs the Python virtual machine.
• Jython Python's Java implementation, Jython will dynamically compile Python code into Java bytecode, and then run on the JVM
• IronPython Python's C # implementation, IronPython compiles Python code into C # bytecode and then runs on the CLR (similar to Jython)
• Python implemented by PyPy (special) Python, which compiles Python bytecode into machine code
• Rubypython, Brython

Python environment

To install Python:

Windows:

1. Download the installation package: https://www.python.org/

2. Install the default installation path: C:\python27

3. Configure environment variables: "Right-click Computer"-"Properties"-"Advanced system Settings"-"Advanced"-"Environment variable"-"in the second content box to find the variable named path of a row, double-click"-"Python installation directory appended to the variable value, with; such as: the original value; C:\python27, remember that there is a semicolon in front

Linux:

1. No installation, original Python environment PS: If bring 2.6, please update to 2.7

Update Python:

Windows: Load Unloading

Linux:linux Yum relies on its own python, to prevent errors, the update here is actually to install a python

View the default Python version

Python-v

1. Install gcc for compiling python source: Yum install gcc

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

3. Unzip and enter the source file

4. Compiling the installation

./configure

Make all

Make install

5. View version

/usr/bin/local/bin/python2.7-v

6. Modify the default Python version

mv/usr/bin/python/usr/bin/python2.6

In-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

#! the head /usr/bin/python modified to #! /usr/bin/python2.6

Getting Started with Python

One, the first Python code

Create the hello.py file under the/home/dev/directory, as follows:

Execute the hello.py file, i.e.: python/home/dev/hello.py

The Python content executes as follows:

II: Interpreter

When executing python/home/dev/hello.py in the previous step, it is clear that the hello.py script is executed by the Python interpreter. If you want to execute a python script like Jade execution shell script, for example:./hello.py, then you need to specify the interpreter in the header of the hello.py file, as follows:

As a result, execute:./hello.py.

PS: Need to give hello.py execute permission before execution, chmod 755 hello.py

Third, Content coding

Tell the Python interpreter what code to use to execute the source code, i.e.:

Iv. notes

When line comment: #被注释的内容

Multiline Comment: "" "Annotated Content" ""

V. Execute script incoming parameters

Python has a large number of modules, which makes developing Python programs very concise. There are three types of class libraries:

• Python-supplied modules
• Industry-Open Source modules
• Modules developed by programmers themselves

Python provides a sys module inside, where SYS.ARGV is used to capture parameters passed in by the Python script

Vi.. pyc file

When you execute a python code, if you import a different. py file, it is automatically generated with the same name as the execution. PYC file, which is the bytecode generated by the Python interpreter after compilation.

PS: Code is compiled to generate bytecode, and bytecode can be obtained by decompile.

Seven, variable

1. Declaring variables

The code above declares a variable named: Name, and the value of the variable name is: "Zhangsan"

The role of a variable: a nickname that refers to what is stored in an address in memory

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 ', ' Finall Y ', ' for ', ' from ', ' global ', ' if ', ' import ', ' in ', ' was ', ' lambda ', ' not ', ' or ', ' pass ', ' print ', ' raise ', ' return ', ' Try ', ' While ', ' with ', ' yield '}

2. Assigning values to variables

Eight, input

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

IX: Process Control and indentation

Requirement One, user login verification

Demand two, according to the user input content output its permissions

• 1.if conditions:

code block

Else:

code block

• 2.if conditions:

code block

Elif conditions:

code block

Else

code block

• 3. Conditions

True False

1 > 2 n1 > N2 n1==n2

Name = = "Alsex" or "name = =" Zhao "

Name! = "Zhao"

Name = = "Zhao" and pwd= "123"

Ten, while loop

1. Basic cycle

2.break

Break to exit all loops

3.continue

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

Python Development (second article): Initial python