python in the dictionary to create and access

Disclaimer: This article is a blogger original article, shall not be reproduced without the bloggers allowed. https://blog.csdn.net/sehanlingfeng/article/details/90994147

# 字典的创建

a = {
    1: 'a',
    2: 'b',
    '3': 'c'
}

# 作为字典key,必须是不可改变的数据类型

l1 = [1, 2, 3]

b = {
    l1: 1                           # 列表不能作为字典的key
}

t1 = (1, 2, 3)
l1 = [1, 2, 3]

c = {
    t1: l1              			# 元组可以作为字典的key
}

print(c)                			# {(1, 2, 3): [1, 2, 3]}


d = dict()              			# 字典的另一种创建方式dict
print(d)                			# {} 空字典

e = dict(a=1, b=2, c='a')

print(e)                			# {'a': 1, 'b': 2, 'c': 'a'}

# 字典的访问

print(e['a'])           			# 1 打印字典e中key为a的value:1

# 字典可以被改变

e['d'] = 123            			# 给字典新加一个key

print(e)                			# {'a': 1, 'b': 2, 'c': 'a', 'd': 123}

e['d'] = 3              			# 改变key为d的value值:改成3

print(e)                			# {'a': 1, 'b': 2, 'c': 'a', 'd': 3}

# 一个字典不能成为另一个字典的key,因为字典能够被该改变