Python variables and data types (study notes)

Variables and data types

variable:

# a  我们就称之为变量 （使用一个名字 来代替一段内容）

a = "你好"
print(a)

Why do we use variables?

If we say: we have the following code

print("你好")
print("你好")
print("你好")
print("你好")
print("你好")

We want to change "Hello" to Hi, so we can only change one by one. If we use variables

Define an a=Hi, put what you want in a, but the variables are also standardized

a="Hi"

print(a)
print(a)
print(a)
print(a)
print(a)

But why does this report an error? Why some can be used and some cannot be used

c = yes
print(c)

This involves the concept of data types

In our Python, the data has its own corresponding type:

# 数字类型 ：  整数型 int  浮点型float   复数 complex
print(45)      # int整数类型
print(3.1415)  # float浮点类型
print((-1) ** 0.5)   # 复数 complex

# 字符串类型  python里的字符串要求使用一对单引号，或者双引号来包裹
print("我一只小鸭子，咿呀咿呀吆")
print('门前大桥下，游过一群鸭')

# 布尔类型   表示 真假 / 对错（注意大小写）
# 只有两个值 True 和 False
print(5 > 3)  # True
print(5 > 9)  # False

# 列表类型
names = ['拉拉','哈哈','嘻嘻','哼哼']
# 字典类型
person = {
    
    'name':'李奎','age':22,'addr':'山东'}
# 元组类型
num=(1,2,3,4,5,6)
# 集合类型
j={
    
    9,'你好',True,9.2}

print('门前大桥下，游过一群鸭')

type of data:

View data type:

Use the type built-in class to view the data type of the current variable

a = 34
b = '你好'
c = True
d = {
    
    '早','啊','队','长'}
e = ['啦啦','哈哈','嘻嘻']
f = (1,2,3,4)
# 使用type内置类可以查看当前变量的数据类型
print(type(a))
print(type(b))
print(type(c))
print(type(d))
print(type(e))
print(type(f))

# 在Python里变量是没有数据类型的
# 我们所说变量的数据类型，其实是变量对应的值的数据类型
m = 23;
print(type(m))
m= "HI"
print(type(m))