Python中的变量和数据类型使用方式

message = "Hello, World!"
print(message)

a = 10
b = 3.14
c = 2 + 3j

print(a + b)  # 输出 13.14
print(a * b)  # 输出 31.4
print(c.real)  # 输出 2.0
print(c.imag)  # 输出 3.0

name = "John"
age = 25

message = "My name is " + name + " and I am " + str(age) + " years old."
print(message)  # 输出 My name is John and I am 25 years old.

fruits = ['apple', 'banana', 'orange']
print(fruits[1])  # 输出 banana

fruits.append('pear')
print(fruits)  # 输出 ['apple', 'banana', 'orange', 'pear']

fruits.remove('banana')
print(fruits)  # 输出 ['apple', 'orange', 'pear']

numbers = (1, 2, 3, 4, 5)
print(numbers[2])  # 输出 3

person = {'name': 'John', 'age': 25, 'city': 'New York'}
print(person['city'])  # 输出 New York

person.update({'gender': 'male'})
print(person)  # 输出 {'name': 'John', 'age': 25, 'city': 'New York', 'gender': 'male'}

del person['age']
print(person)  # 输出 {'name': 'John', 'city': 'New York', 'gender': 'male'}

numbers = {1, 2, 3, 4, 5}
print(3 in numbers)  # 输出 True

numbers.add(6)
print(numbers)  # 输出 {1, 2, 3, 4, 5, 6}

numbers.remove(4)
print(numbers)  # 输出 {1, 2, 3, 5, 6}

a = "123"
b = int(a)
c = str(b)

print(a, type(a))  # 输出 123 <class 'str'>
print(b, type(b))  # 输出 123 <class 'int'>
print(c, type(c))  # 输出 123 <class 'str'>