Question

以下Python List Comprehension语句可以改为下面的for循环。

>>> [(x,y) for x in range(5) if x % 2 == 0 for y in range(5) if y % 2 == 1]

>>> result = []
>>> for x in range(5):
    if x % 2 == 0:
        for y in range(5):
            if y % 2 == 1:
                result.append((x,y))

我很难理解以下两个列表理解表达式循环（更易于阅读）表达它们的方法是什么？

[(min([row[i] for row in rows]),max([row[i] for row in rows])) 
for i in range(len(rows[0]))]

[[random.random()*(ranges[i][1]-ranges[i][0])+ranges[i][0] 
for i in range(len(rows[0]))] for j in range(k)]

Answer 1

使用你的风格：

我相信第一个这样做：

result = []
for col in range(len(rows[0])):
    a = rows[0][col]
    b = rows[0][col]
    for row in rows:
        a = min(a, row[col])
        b = max(b, row[col])

    result.append((a, b))

Answer 2

以下是展开第一个循环的示例，请参见此处：http://codepad.org/cn0UFPrD

rows = [[1,2,3,4],[3,5,88,9],[4,55,-6,0],[0,34,22,1222]]
t1 = [(min([row[i] for row in rows]),max([row[i] for row in rows])) for i in range(len(rows[0]))]
print(t1)

# Easy loop
t2 = []
for i in range(len(rows[0])):
    innerElements = []
    for row in rows:
        innerElements.append(row[i])
    newTuple = ( min(innerElements),max(innerElements) )
    t2.append(newTuple)

print(t2)

你可以用同样的方式扩展第二个循环。

等价于复杂列表理解的循环表达式

2 个答案: