大蟒蛇python教程共享Python的列表推导式你了解吗

[expression for target in iterable]  

[expression for target in iterable if condition]

[expression for target1 in iterable1 if condition1  			for target2 in iterable2 if condition2  						...  			for targetn in iterablen if conditionn]  

x = [1, 2, 3, 4, 5]  x = [i * 2 for i in x]  print(x)    # [2, 4, 6, 8, 10]  

y = [i for i in range(10)]  print(y)    # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]  

# 获取矩阵第二列  matrix = [      [1, 2, 3],      [3, 5, 6],      [7, 8, 9]  ]  col2 = [row[1] for row in matrix]  print(col2)    # [2, 5, 8]  

# 获取矩阵主对角线元素  matrix = [      [1, 2, 3],      [3, 5, 6],      [7, 8, 9]  ]  diag = [matrix[i][i] for i in range(len(matrix))]  print(diag)    diag2 = [matrix[i][len(matrix) - i - 1] for i in range(len(matrix))]  print(diag2)    # [1, 5, 9]  # [3, 5, 7]  

# 创建内嵌列表  a = [[0] * 3 for i in range(3)]  print(a)  a[1][1] = 5  print(a)    # [[0, 0, 0], [0, 0, 0], [0, 0, 0]]  # [[0, 0, 0], [0, 5, 0], [0, 0, 0]]  

# 20以内偶数列表  b = [i for i in range(20) if i % 2 == 0]  print(b)    # [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]  

# 筛选f开头的单词  words = ['great', 'fishc', 'brilliant', 'excellent', 'fantistic']  res = [word for word in words if word.startswith('f')]  print(res)    # ['fishc', 'fantistic']  

# 展开二维列表  matrix = [      [1, 2, 3],      [4, 5, 6],      [7, 8, 9]  ]  flatten = [col for row in matrix for col in row ]  print(flatten)    # [1, 2, 3, 4, 5, 6, 7, 8, 9]  

flatten = []  for row in matrix:  	for col in row:  		flatten.append(col)  

# 笛卡尔积  fulljoin = [x + y for x in '12345' for y in 'abcde']  print(fulljoin)    # ['1a', '1b', '1c', '1d', '1e', '2a', '2b', '2c', '2d', '2e', '3a', '3b', '3c', '3d', '3e', '4a', '4b', '4c', '4d', '4e', '5a', '5b', '5c', '5d', '5e']  

ans = [[x, y] for x in range(10) if x % 2 == 0 for y in range(10) if y % 3 == 0]  print(ans)    # [[0, 0], [0, 3], [0, 6], [0, 9], [2, 0], [2, 3], [2, 6], [2, 9], [4, 0], [4, 3], [4, 6], [4, 9], [6, 0], [6, 3], [6, 6], [6, 9], [8, 0], [8, 3], [8, 6], [8, 9]]