Python basics ---- basic concepts and knowledge, python ----

Python basics ---- basic concepts and knowledge, python ----

Sort out the basic concepts and knowledge of python, and use python3 as the syntax standard.

 

Python Introduction

An Object-Oriented explanatory computer design language with rich and powerful libraries.

• Python positioning: "elegant", "clear", and "simple"
• Multiple application scenarios: Write tools, backend services, and mobile terminals.

Build running environment

Download the corresponding version of Python installation. The official website address is as follows:

https://www.python.org/

Run a get-pip.py to install pip (Py3 comes with pip)

https://bootstrap.pypa.io/get-pip.py

Add the python directory and Scripts subdirectory to the Environment Variable

 

Install Virtual Environment

• Install virtualenv

pip install virtualenv

• If the configuration is correct, the python interpreter interface is displayed.

Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:01:18) [MSC v.1900 32 bit (Intel)] on win32Type "help", "copyright", "credits" or "license" for more information.>>>

 

Select Editor

Sublime Text, Wing IDE, pycharm

 

Basic syntax and concepts

Variable

>>> x=3>>> x*26>>> x*9992997

　　

Integer and floating point number

X = 567 (integer) y = 5.67 (floating point number) x/y (default return floating point number) x // y (default return integer)

　　

Function

Def checkIsHasCapitalLetter (filename): if filename. islower () = True: return True else: common. outError (filename + "the file name is capitalized ................. ") return Fasle

　　

Indentation, process control statements for, if, while, etc. all rely on Indentation recognition, and functions are also

for i in range(0, 5):    print(i)

Module

>>> Import common (allow namespaces to access things in common) >>> common. count () >>> from common import count (added to the current namespace) >>> count ()

　　

Run the python Program

python.exe test.py

Common Data Structures

• List)
• Dictionary (dict)
• Set)
• Tuple)

Common Data Types

• Integer
• Floating Point Number
• Boolean Value
• String

String Basics

The string cannot be changed. It is the same as java. If a value is assigned, a new string is created.

String definition, which can be single quotation marks or double quotation marks. + is used for character concatenation.

>>> "Hello world" 'Hello world' >>> "hello" + "world" 'helloworld' >>> "don 'tlet go "" don't let go ">>> 'Don \'t let go '(escape single quotes) "don't let go" >>> "don \'t let go" "don't let go" >>> r "don \'t let go" (front "r" does not escape) "don \'t let go"

　　

String search

>>> "nothing to see here".find("see")11>>> "nothing to see here".find("ok")-1

　　

String formatting

>>> filename = "notepad">>> "get file: %s ok"%filename'get file: notepad ok'

UNICODE, python3 string is Unicode encoded
1. convert other string formats to unicode:

ret=str.decode("gb2312")ret=str.decode("ascii")ret=str.decode("utf-8")

2. Convert unicode characters to other string formats:

ret=str.encode(“gb2312”)ret=str.encode("ascii")ret=str.encode("utf-8")

Regular Expression

http://www.cnblogs.com/huxi/archive/2010/07/04/1771073.html

　

Extension

String built-in functions, len (), split (), upper (), strip () multi-line string subscript [0], [-2]