63.字典推导式

字典推导式

字典推导式语法和列表推导式语法类似:

my_dict = { expr for value in collection if condition }

我们下面将两个列表转换成一个字典:

keys = ['a', 'b', 'c', 'd']
vals = [10, 20, 30, 40]
my_dict = {key: value for key, value in zip(keys, vals)}
print(my_dict)

例子1：

# 01:
# 准备两个列表
keys = ["a", "b", "c", "d"]
values = [1, 3, 5, 7]

# 定义一个字典(空字典)
my_dict = {}

# 循环
for i, key in enumerate(keys):
    # 添加元素
    my_dict[key] = values[i]
print(my_dict)

运行结果：

{'a': 1, 'b': 3, 'c': 5, 'd': 7}

例子2：

import sys


# 02: zip函数
a = [1, 2, 3]
b = [4, 5, 6]
c = [7, 8, 9]
# 计算a b c 分别占用了多少内存空间
# 占用88字节
# 1024字节 = 1kb
print(sys.getsizeof(a))
print(sys.getsizeof(b))
print(sys.getsizeof(c))

运行结果：

88
88
88

例子3：

import sys


# 02: zip函数
a = [1, 2, 3]
b = [4, 5, 6]
c = [7, 8, 9]
# 计算a b c 分别占用了多少内存空间
# 占用88字节
# 1024字节 = 1kb
# print(sys.getsizeof(a))
# print(sys.getsizeof(b))
# print(sys.getsizeof(c))
# 压缩
my_zip = zip(a, b, c)
print(sys.getsizeof(my_zip))
print(list(my_zip))

运行结果：

64
[(1, 4, 7), (2, 5, 8), (3, 6, 9)]

例子4：

import sys


# 02: zip函数
a = [1, 2, 3]
b = [4, 5, 6]
c = [7, 8, 9]
# 计算a b c 分别占用了多少内存空间
# 占用88字节
# 1024字节 = 1kb
# print(sys.getsizeof(a))
# print(sys.getsizeof(b))
# print(sys.getsizeof(c))
# 压缩
my_zip = zip(a, b, c)
# print(sys.getsizeof(my_zip))
# print(list(my_zip))
# # 解压缩
a1, b1, c1 = zip(*my_zip)
print(a1)
print(b1)
print(c1)

运行结果：

(1, 2, 3)
(4, 5, 6)
(7, 8, 9)

例子5：

# 03: 字典推导式
# 准备两个列表
keys = ["a", "b", "c", "d"]
values = [1, 3, 5, 7]
# my_zip = zip(keys, values)
# print(list(my_zip))
my_dict = {k:v for k, v in zip(keys, values)}
print(my_dict)

运行结果：

{'a': 1, 'c': 5, 'b': 3, 'd': 7}

例子6：

import sys



# 04:
# 列表推导式
my_list = [i for i in range(10000)]
print(sys.getsizeof(my_list))
# 生成器
g = (i for i in range(10000))
print(type(g))
print(sys.getsizeof(g))

运行结果：

87624
<class 'generator'>
88