语法
1.普通
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[expression for target in iterable] |
2.带条件
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[expression for target in iterable if condition] |
3.嵌套
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[expression for target1 in iterable1 if condition1 for target2 in iterable2 if condition2 ... for targetN in iterableN if conditionN] |
实例
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x = [ 1 , 2 , 3 , 4 , 5 ] x = [i * 2 for i in x] print (x) # [2, 4, 6, 8, 10] |
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y = [i for i in range ( 10 )] print (y) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] |
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# 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] |
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# 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] |
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# 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]] |
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# 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] |
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# 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'] |
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# 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] |
等价于
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flatten = [] for row in matrix: for col in row: flatten.append(col) |
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# 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'] |
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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]] |
总结
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原文链接:https://blog.csdn.net/cold___play/article/details/123638695