# python data types and operators

First, python type judgment

type, isinstance

type (variable or constant): return data type

a = 23.3 print(type(a)) b = 2e3 print(b, type(b)) outputs:

2000.0

isinstance(variable or constant, data type name) Determine the data type. Returns true if it is the specified data type, otherwise returns false

a = 10 if isinstance(a, int): print("a is an integer")

Second, python data types are divided into built-in types (types supported by the language itself) and custom types, classes.

Common built-in types include:

1. Numerical type

- Integer int, representing the integer type. For example: 3,4,5
- A floating-point number float, representing a real number. There are 2 ways of writing: natural notation and scientific notation

Natural notation: 2.3, 4.5

Scientific notation: 2e2 means 200. e refers to an exponent with base 10, and e must be followed by an integer

a = 23.3 print(type(a)) b = 2e3 print(b, type(b)) outputs:

2000.0

- complex number complex 2+3j

c = 3 + 2j print(c, type(c)) output: (3+2j)

2. Boolean type

The Boolean type represents true and false, right and wrong, yin and yang, etc. As long as it is two states, it can be represented by the Boolean type. It has two values: True(1) and False(0)

Arithmetic operations that can be performed on numbers and booleans

a = 3

b = 3.5

c = True

print(a + c)

print(c * 5)

3. String type

Strings enclosed in quotation marks

'single quoted string'

'double quoted string'

'''

multiline string

'''

"""

multiline string

"""

Escape the string, if the single quote contains a single quote, then the single quote inside needs to be escaped

escape character description escape character description

\' represents an ordinary character single quote

\rEnter

\"represents an ordinary character double quotation mark

\nNewline

\''' an ordinary triple single quote

\\ an ordinary character

\\"""A normal triple double quotation mark

\ttab key

3. Operators and expressions (expressions have no value)

1. Arithmetic operators include: + - * / //(divide) %(modulus, remainder) **(exponent)

The purpose of the modulo operator: judging parity, judging whether it can be divisible, the greatest common divisor, daffodil number

2. Function

- math function

- random function

The random function is introduced into the random library

import random print(random.randint(1,100)) Random integers between 1 and 100, before and after the package print(random.random()) Random decimals between 0 and 1, without print(random. randrange(1,100,2)) Output random numbers with a step size of 2 between 1 and 100, output before and after the packet : 33 0.05559590353134125 21

3. Assignment operator

= += -= *= /=

The left side of the assignment operator must be a variable

4. Relational Operators

Relational operators are comparison operators, and the result is a boolean value

Exercise:

1. Convert Fahrenheit to Celsius

C = float(input()) F = 1.8 * C + 32 print(F)

2. Solve the first-order equation ax+b=0, enter the values of a and b, and solve x

a = int(input("Please enter the coefficient a of the linear equation:")) b = int(input("Please enter the constant b of the linear equation:")) print("The root of the linear equation %dx+%d=0 is : x=%d"%(a, b, (0 - b)/a)) output please enter the coefficients of the linear equation a: 2 please enter the constants of the linear equation b: 6 the root of the linear equation 2x+6=0 is : x=-3 3. Write a program to receive the names, math scores and computer scores of 2 students input from the keyboard, store the chalk into 6 variables, and then print out the names and total scores of the 2 students

name1 = input("请输入同学a的名字：")name2 = input("请输入同学b的名字：")core1 = float(input("请输入同学a的数学成绩："))core2 = float(input("请输入同学b的数学成绩："))core3 = float(input("请输入同学b的计算机成绩："))core4 = float(input("请输入同学b的计算机成绩："))core_all = core1 + core2 + core3 + core4print("同学%s和同学%s的总成绩为：%.0f"%(name1, name2, core_all))print("同学%s和同学%s的总成绩为：%.2f"% (name1, name2, (core1 + core2 + core3 + core4)))

4.编写一程序，对用户输入的两个数据a和b，输出交换后的a和b的值

a = int(input("请输入值a:"))b = int(input("请输入值b:"))a, b = b, aprint("分别输出a和b的值：%d,%d"%(a, b))

5.从控制台输入2个数，输出较大的值

a = int(input("please enter the value a:")) b = int(input("please enter the value b:")) print("please output the maximum value: %d"% max(a, b)) 6 .Enter an integer from the keyboard to determine whether the number is divisible by 3

a = int(input("Please enter the value a:")) if a % 3 ==0: print("Divisible by 3") 7. Input a 3-digit number from the keyboard, and find the difference of each number of the three-digit number and

a = int(input("Please enter a three-digit integer a:")) gewei = a % 10 shiwei = a // 10 % 10 baiwei = a // 100 print("The sum of the digits is: %d"% (gewei + shiwei + baiwei))

8. Enter a three-digit number from the console, if it is the number of daffodils, it will print"is the number of daffodils", otherwise it will print"not the number of daffodils"

a = int(input("Please enter a three-digit integer a:")) gewei = a % 10 shiwei = a // 10 % 10 baiwei = a // 100 if gewei**3 + shiwei**3 + baiwei** 3 == a: print("is the number of daffodils") else: print("is not the number of daffodils")

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