Python - non-clumsy way to enumerate over filtered dictionary-CodePudding

I have a code like this (d is some dictionary and s is some set):

for i, (k, v) in enumerate((k, v) for k, v in d.items() if k in s):
    ...

Even if we ignore the ugly repetition, all literals actually have substantial length, so repeating k and v 3 times is not an option. What's the best way to write it? Right now, we use the following (also ugly) option:

i = -1
for k, v in d.items():
    if k not in s:
        continue
    i  = 1
    ...

Another option:

for i, (k, v) in enumerate((k, d[k]) for k in d if k in s):
    ...

, but it basically has the same amount of repetitions.

I'm OK with using any library which is shipped by default (i.e. without pip install).

CodePudding user response：

With one extra line, but much less complexity, you could do:

for i, k in enumerate(filter(s.__contains__, d)):
    v = d[k]

A variation of this uses set intersection (that may scramble your insertion order though):

for i, k in enumerate(s & d.keys()):
    v = d[k]

CodePudding user response：

dict comprehension is the fastest way to filter a dict:

filtered_dict = {key: value for key, value in d.items() if key in s}

Therefore, I would suggest to define a task function that does the job on the items and do everything inside this dict comprehension:

def task(key, value):
    # do the required job on the dict items
    ....
    return result


{key: task(key, value) for key, value in d.items() if key in s}

The result is a dict that contains the computed result for each key/value item. Of, course, you can add enumerateif an index is required in addition.