python列表推导式详解

1、概念

轻量级循环创建列表

# 01: 需求: 创建一个列表100个元素 1~100
# my_list = []
# for i in range(1, 101):
#     my_list.append(i)

# my_list = [i for i in range(1, 101)]
# print(my_list)

# 02: 需求: 创建一个列表 10个元素, '中国'
# my_list = []
# for _ in range(10):
#     my_list.append('中国')

# my_list = ['中国' for _ in range(10)]
# print(my_list)

# 03: 需求:定义一个列表 保存1~100之间的偶数
# my_list = []
# for i in range(1, 101):
#     if i % 2 == 0:
#         my_list.append(i)

# my_list = [i for i in range(1, 101) if i % 2 == 0]
# print(my_list)

# 04: 需求: [(0, 1), (0, 2), (0, 3), (1, 1), (1, 2), (1, 3)]
# my_list = []
# for i in range(2):
#     for j in range(1, 4):
#         my_list.append((i, j))

# my_list = [(i, j) for i in range(2) for j in range(1, 4)]
# print(my_list)

# for i in range(2):
#     for j in range(1, 4):
#         print(j)

 

# 请写出一段 Python 代码实现分组一个 list 里面的元素,比如 [1,2,3,...100]变成 [[1,2,3],[4,5,6]....[100]]

# [1,2,3,...100]
a = [i for i in range(1, 101)]
# [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
#  0, 1, 2, 3, 4, 5, 6, 7, 8, 9
#  0
# [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]

# [1, 2, 3] -> 0
# ret1 = a[0:3]
# print(ret1)
# # [4, 5, 6] -> 3
# ret2 = a[3:6]
# print(ret2)
# # [7, 8, 9] -> 6
# ret3 = a[6:9]
# print(ret3)
# # [10]      -> 9
# ret4 = a[9:12]
# print(ret4)

# x = 0
# 公式: a[x:x+3]

# # 定义一个空的列表
# b = []
# # 拿到变量a的下标索引
for x in range(0, len(a), 3):
    pass
#     b.append(a[x:x+3])

# b = [a[x:x+3] for x in range(0, len(a), 3)]
# print(b)