Getting Started with Python learning notes 1:python

About the selection of versions

According to the internet, if Python is to be used at work, choose version 2.7. Here I choose 2.7.9 version of to study;

What is Python?

is a high-level computer programming language. Wide range of applications, Google and other famous companies are in use.

Python, the English word, is the serpent, the script;

Disadvantages:

1, the execution speed is slow, because is the high-level language, translates into the machine language the cost limit, appears the speed relative to other languages to be slow;

2, unable to encrypt the code, because it is an explanatory language;

Install Python

System type	Installation method	Description
MaxOS		OSX 10.8 or more comes with Python
Linux		How to install the basic software
Windows	Https://www.python.org/ftp/python/2.7.9/python-2.7.9.msi	Set to Path

Python's Interpreter

Interpreter version	Description
CPython	The official interpreter, written in C, is the python that runs under the command line.
Ipython	Interactive interpreter, based on CPython, with improved interactivity
PyPy	Focus on execution speed, based on JIT technology
Jython	Python interpreter running on the Java platform
IronPython	Python interpreter for the dotnet platform

The most widely used is CPython, if you want to interact with the Java and Dotnet platforms using network tuning to interact better.

The first Python program

Open the command line, enter Python, and enter the CPython interpreter;

Command	Description
100+200	Simple calculation
print ' Hello,world '	Output string
Exit ()	Exit the Python Interpreter

You can also use a text editor, we recommend the use of notepad++, note that the encoding type is saved as Utf-8 no BOM format;

print ' Hello, Python '; a=100+200 Print A; Exit ()

To run the command:

Python hello.py

Operating effect:

Input and output

Output method print ' string ', using commas to separate multiple strings, comma equivalent to a space;

Input: raw_input (' input hint text '); get string;

Python Basics

Python is indented, #开头的语句数注释; When the statement ends with a colon: The indented statement is a block of code and is sensitive to case;

Data type

The data types that Python can handle directly have a centralized

Type	Description
Integral type	Any size, plus or minus.	Divided into decimal and hexadecimal ox
Floating point number	Contain decimals	Scientific notation can be used
String	Use any character enclosed in ' or '	Use \ to identify escape characters Multiple lines can be labeled with ' ... '
Boolean value	Two kinds of values for True,false tour	Boolean operations can be performed, And,or,not
Patyon also provides a variety of data types, such as lists, dictionaries, and also supports custom data types
Null value	None ID, cannot represent 0
Variable	Can be any type, defined directly by an assignment symbol, which actually defines a pointer or address.	Python is a dynamic language, Java is a static language
Constant	Variables that cannot be changed

String encoding

Coding	Range	Number of bytes	Advantage
Ascii	English letters and numbers	1 bytes	Simple, small storage space
Unicode	Characters in all languages	4 bytes	Wide Coverage
UTF8	Characters in all languages	Depending on the situation, letters and numbers use 1 bytes, and other characters use the number of bytes as needed	Space saving

File processing: Load into memory display using Unicode encoding, save to file using UTF8 encoding;

Browser processing: Server-to-Web transmission via UTF8 encoding;

ASCII-related functions:

Function	Function description
Ord (' B ')	Get the corresponding number
Chr (65)	Get the corresponding character

Unicode characters u ' hello '

Convert to UTF8 code: Encode (' Utf-8 ')

Gets the string length len (' string ')

Convert to Unicode encoding decode (' Utf-8 ')

Common comments

#!/usr/bin/env python

#-*-Coding:utf-8-*-

The first line is to tell the Linux/os system that Python is an executable program that Windows ignores;

The second line is to tell the Python interpreter to read the source file according to UTF-8 code, otherwise it may be garbled in Chinese

Formatting:

Placeholder	Type
%d	Integer
%f	Floating point number
%s	String
%x	Hexadecimal number

Common data structures

Data	Characteristics	Common operations	Initialize method
List	An ordered array of variable lengths that can construct a multi-bit array	Append, append Element Pop deletes the last one, or the element at the specified position Insert a position inserts an element Len Get length A "I" gets an element, and when I is a negative number, the inverse is obtained.	[' A ', 123, ' shit ']
Tuple	Length, point to immutable ordered array, more secure	B "I" value by position	(' A ', 789,[1, ' end ')
Dict	MAP, high query efficiency, but low storage efficiency	In is present Get getting elements Pop "key" delete element c[' key ') to get a value or add value based on key	{' name ': ' Carter ', ' Age ': 27}
Set	A collection in algebra	Add add Element Remove delete Element	Set ([1,2,3,4])
Immutable objects	Is that objects cannot be changed, pointing can change

Condition and cycle judgment

Description

TD valign= "Top" width= "280" >

Kind	format
Conditional judgment	If If ... Else If...elif...else	Elif from top to bottom As long as X is a non-0 number, not an empty string, a non-empty list, Condition can be true
Loop judgment	for V AR in array: while (condition):	 
#-*-coding:utf-8-*--*- age=3 If age >=: print ' adult ' else: print ' teenager ' sum = 0 For x in range (101): Sum+=x; Print sum; Sum = 0 N = While n>0: Sum +=n N-=2 Print U ' 100 within the even-numbered addition to get ', sum

Range (num) a list from 0 to Num-1

int (' string ') converts the string to an integer

Getting Started with Python learning notes 1:python