Python概述了用于将函数应用于元素列表的不同技术

Question

我想了解python3.X中使用的以下技术的以下结果来执行某些操作。请考虑以下使用不同技术的代码尝试获得相同的结果。

def addSlash(fname):
    if isinstance(fname, str):
        if " " in fname:
            return fname.replace(" ", "\ ")


# example output
a = "ab c"
a = addSlash(a)
print(a)
print()


# list of interest
files = ["spaces file1", "spaces file2", "spaces file3"]

for f in files:
    f = addSlash(f)
    # this prints correct result but list elements are not permanently having the change.
    print(f)

print('\nThis did not change..')
print(files)


print('\nTrying the old way gives 2 slashes as well..')
files = ["spaces file1", "spaces file2", "spaces file3"]
for i in range(0, len(files)):
    files[i] = addSlash(files[i])
print(files)

print('\nTrying this way give as different results, putting 2 slashes instead of one for some reason')
files = ["spaces file1", "spaces file2", "spaces file3"]
files = [addSlash(f) for f in files]
print(files)

print('\nSame with this one, same results as above.')
files = ["spaces file1", "spaces file2", "spaces file3"]
f = list(map(lambda x: x.replace(" ", "\ "), files))
print(f)

运行时上述输出如下：

ab\ c

spaces\ file1
spaces\ file2
spaces\ file3

This did not change..
['spaces file1', 'spaces file2', 'spaces file3']

Trying the old way gives 2 slashes instead of one!
['spaces\\ file1', 'spaces\\ file2', 'spaces\\ file3']

Trying this way give as different results, putting 2 slashes as well!
['spaces\\ file1', 'spaces\\ file2', 'spaces\\ file3']

Same with this one, same results as above.
['spaces\\ file1', 'spaces\\ file2', 'spaces\\ file3']

有人可以对每种技术发表评论并解释它为什么不起作用吗？