通过列表理解修改列表中的列表

Question

我怎样才能理解这些 loops 和 if statements？

raw = [['-', 'bla'], ['-', 'la'], ['=', 'bla']]

for one in raw:
    if one[0] == '-':
        for two in raw:
            if two[1] == one[1] and two[0] == '=': two[0] = '--'

到目前为止：

[two+one for two in raw for one in raw]

但不确定将 if 语句放在哪里：

if one[0] == '-' 和 if two[1] == one[1] and two[0] == '=': two[0] = '--'

Answer 1

一个简单的列表理解就足够了：

raw = [['-', 'bla'], ['-', 'la'], ['=', 'bla']]

res = [['--' if (i != '-') and (['-', j] in raw) else i, j] for i, j in raw]

结果：

[['-', 'bla'], ['-', 'la'], ['--', 'bla']]

Answer 2

您可以在列表理解中设置项目，

您的代码：

for one in raw:
    if one[0] == '-':
        for two in raw:
            if two[1] == one[1] and two[0] == '=': two[0] = '--'

convert to list comprehension :

[[two.__setitem__(0,'--') if two[1]==one[1] and two[0]=='=' else two for two in raw] if one[0]=='-' else one for one in raw]
print(raw)

输出：

[['-', 'bla'], ['-', 'la'], ['--', 'bla']]

通过列表理解修改列表中的列表

Modifying lists within lists via list comprehension

python

list-comprehension

nested-loops

python-3.x