Python Learning Notes Day02

Article Directory

• variable
• Declare Variables
• Variable Naming Specification
• data type
• Six Types
• Number Type===Number Type
• Int Type===Integer
• Mode 1: Decimal declaration
• Mode 2 binary declaration
• Mode 3: Octal declaration
• Mode 4 hexadecimal declaration
• Float Type===Float Type
• Method 1: Declare with decimals
• Method 2: Scientific Counting
• Bool Type===Boolean
• Complex Type===Complex Number
• Method 1: Use an expression
• Method 2: Use specific functionality
• String Type===String Type
• Method 1: Single quotation mark declaration string `'`
• Method 2: Double quotation mark declaration string `''
• Method 3: Three quotation marks declare the string `''''''` or `''''``
• Selection of String Declarations
• Escape Characters: Changing the Meaning and Function of Characters
• Common escape characters
• Metacharacter: Output in a string-defined format without escaping any escape characters
• Enter key is not a return symbol
• List Type===List Type
• Declaration List
• Tuple Type===Tuple Type
• Tuple declaration
• Set Type===Set Type
• Collection declaration
• Dict Type===Dictionary Type

Container to store data for richer storage

Declare Variables

Variable name = Data

Variable Naming Specification

• Cannot use Chinese, English is recommended

• Variables can use numbers but cannot start

• Variable names cannot use special symbols, but can be underlined_

• Case sensitive

• Variable names need to be meaningful

• Cannot conflict with keyword

There are countless types of Python

Six Types

Number Type===Number Type

Integer is also an integer

Keyword: int or integer

0~9

Sample Code

intvar = 250 print(intvar) print(type(intvar))

Run Results

250 <class 'int'>

0 1

Sample Code

intvar = 0B10001 print(intvar) print(type(intvar))

Run Results

0~7

Sample Code

intvar = 0o147 print(intvar) print(type(intvar))

Run Results

103 <class 'int'>

0~9 ABCEDEF

Sample Code

intvar = 0x14af print(intvar) print(type(intvar))

Run Results

5295 <class 'int'>

• Floating point number is decimal

• Keyword: float or real or double

Sample Code

floatvar = 3.1415926 print(floatvar) print(type(floatvar))

Run Results

3.1415926 <class 'float'>

Sample Code

floatvar = 3.5e10 print(floatvar) print(type(floatvar))

Run Results

35000000000.0 <class 'float'>

There are only two values: True and False

Sample Code

boolvar = True print(boolvar) print(type(boolvar)

Run Results

True <class 'bool'>

Sample Code

comvar = 55 + 22j print(comvar) print(type(comvar))

Run Results

(55+22j) <class 'complex'>

Sample Code

comvar = complex(22, 55) print(comvar) print(type(comvar))

Run Results

(22+55j) <class 'complex'>

String Type===String Type

The declaration of a string

Sample Code

strvar = '123' print(strvar) print(type(strvar))

Run Results

123 <class 'str'>

Sample Code

strvar = "123" print(strvar) print(type(strvar))

Run Results

123 <class 'str'>

Sample Code

strvar = '''123''' print(strvar) print(type(strvar))

Run Results

123 <class 'str'>

• If there are double quotes in the string, it is recommended to declare them in single quotes
• Double quotation marks are recommended if there are single quotation marks in the string
• Triple quotation marks are recommended if the string contains both double and single quotation marks.

Sample Code

strvar = '1\'2\'3' print(strvar) print(type(strvar))

Run Results

1'2'3 <class 'str'>

Sample Code

strvar = 'Abed, I see a silver light,\n Suspected frost on the ground' print(strvar) strvar = 'Look at the bright moon,\r Look down at your home' print(strvar) strvar = 'Look at the bright moon,\t Look down at your home' print(strvar) strvar = 'Look at the bright moon,\ //Look down at your home' print(strvar)

Run Results

Sample Code

strvar = r'Bedside\t bright\'Moonlight\'，\n Doubtfully\'Frost\'' print(strvar) strvar = R'Bedside\t bright\'Moonlight\'，\n Doubtfully\'Frost\'' print(strvar)

Run Results

Under Windows platform:\r\n

On Linux platform:\n

Under Macos platform: \r Before 10.9n After 10.9

List Type===List Type

• Ordered Containers

• The value of a specific item can be modified

Sample Code

# 0 1 2 3 4 listvar = ['army officer's hat ornaments', 'Xishi', 'Yang Yuhuan ', 'Wang Zhaojun', 4] # -5 -4 -3 -2 -1 print(listvar) print(type(listvar)) print(listvar[1]) print(type(listvar[1])) listvar[2] = 'favorite concubine of emperor Minghuang' print(listvar) print(type(listvar))

Run Results

Tuple Type===Tuple Type

• Ordered Containers

• The value of a specific item cannot be modified, and the modification will result in an error.

Specific code

# 0 1 2 3 4 tuplevar = ('army officer's hat ornaments', 'Xishi', 'Yang Yuhuan ', 'Wang Zhaojun', 4) # -5 -4 -3 -2 -1 print(tuplevar) print(type(tuplevar)) print(tuplevar[1]) print(type(tuplevar[1]))

Run Results

Set Type===Set Type

• Unordered combination of a specific set of data

• Data in a collection is not duplicated

• Collection has no order

Sample Code

setvar = {'army officer's hat ornaments', 'Xishi', 'Yang Yuhuan ', 'Wang Zhaojun', 4} print(setvar) print(type(setvar)) setvar = {'army officer's hat ornaments', 'Xishi', 'Xishi', 'Xishi', 'Yang Yuhuan ', 'Wang Zhaojun', 4} print(setvar) print(type(setvar))

Run Results

{4, 'Wang Zhaojun', 'Yang Yuhuan ', 'Xishi', 'army officer's hat ornaments'} <class 'set'> {4, 'Wang Zhaojun', 'Yang Yuhuan ', 'Xishi', 'army officer's hat ornaments'} <class 'set'>

Dict Type===Dictionary Type

• A set of data consisting of keys and values

• Key: character or number

• Value: Any data type

Sample Code

dictvar = {'Pedestrian': 'Wusong', 'Little Cyclone': 'Chaijin', 'Zhiduoxin': 'Wu Yong'} # Key Value print(dictvar) print(type(dictvar)) print(dictvar['Little Cyclone']) #Value can only be checked by key

Run Results

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