First: Getting Started with Python basics

This article is divided into six major categories:

1. About Python

2. Data type

3. Print statement

4. Comments

5. Variable

6. String

First, Python introduction:

python Features: Elegant, clear, concise

Python for development: Web

Python Pros: Less code, faster development

Python disadvantage: The original code cannot be encrypted

Python is a cross-platform programming language that can be run in a language other than a platform

Python version type: 2.7 3.6

Difference: The syntax is incompatible, the 2.7 version can be run directly on the 3.6 version;

Python installation (Windows): 2.7 Configuring environment variables

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Python First Program:

Practice:

print "Hello World" on the screen and enter "exit ()" To complete the first Python program

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Interactive command-line disadvantage: file cannot be saved

Text file with file error ending with. py

Recommended software: Pycharm, nodepad++, never use Notepad, word (because there will be inexplicable errors)

Second, the data type:

1. Integral type

2. Floating-point type

3. Strings (String)

4. Boolean type (True,false)

5. Null value (None)

list, dictionary, custom--The following chapters will refer to

1. Integral type (integer)

Python can handle integers of any size, including negative integers

1,100,-1000,0

The computer uses the binary: 10101010

Hex: 0x and 0-9,a-f indicate for example: 0xff=255

Practice: Use decimal integer 10 to add hex 255 to print out the results;

Print (10+0XFF); 265

2. Floating-point type

Decimals, floating-point numbers can be written in scientific terms: 1230000000.0
For large or very small floating-point numbers, exponential power is used

1.23e9 exponent Power 1.23*10 9 times (less than 10)

Print (1.23e9); 1230000000.0

3. Strings (String)

Any text enclosed in "or" "abc" "XYZ" "10"

Print (' abc ');p rint ("xyz");

4. Boolean value type (True,false)

Boolean values can be represented directly in Python using True,false (note case)

--Practice: Can output Boolean values directly

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5. Null value (None)

Cannot be understood as 0, because 0 is meaningful, and none is a special null value

--Practice:

1. Please use a string to represent the welcome to Beijing

2. Computes the Boolean value of the following expression

100<90//?

0xff==255//?

(Note: = = Indicates whether equality is judged)

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Print statement

Syntax: print ();

Attention:

1. >>> is a Python interpreter prompt, not part of the code

2. Don't add >>> when editing

Print: Multiple strings can be printed, separated by commas, you can wind up a string of output;

--Exercise: Print out what colors your shirt?

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Print also prints integers, or calculates the results

--Practice: 100+200=300

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--Exercise: Print the string in two ways Hello World

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4.Python comments

Comments are used to illustrate the code, to yourself or to others to see

The Python interpreter ignores comments directly while the program is running

#开头, after which the code is counted as comments

5. Variables

What is a variable: literally means the amount that can be changed

Variables in the program in memory open up a space to store data place, and then a name, the name is the variable name.

Variables can store any data and must be assigned when declaring variables

Variable name: Can be arbitrarily taken, but to follow certain rules, must be the case of the English, numeric and underline combination, cannot start with a number

A=100 variable A is an integer

A= ' Hello ' variable A is a string

Variable characteristics: variable itself type is not fixed, Python dynamic voice, the advantages of more flexible

--Practice:

x=10;

x=x+2;

Print (x)//12

Print (x+2)//14

Print (x=x+2)//Error

Print (x==x+2)//false

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--Practice:

A= ' ABC ';

B=a;

A= ' XYZ ';

Print (a); Xyz

Print (b); Abc

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Defining strings in Python

‘’ “”

What if the string itself has quotation marks? I ' m OK single-lead double-lead to wrap each other;

What if the string has both a single quote and double quotes?

Escape character \

Str= ' Kate said ' I ' m OK '

Demand output: Escape character Kate said "I ' m OK"

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First: Getting Started with Python basics