Using map() instead of for loop and writing shorter (better) code

Question

What would be a way to update this for loop to use map() instead, and is possible to shorten the if code too? I will write some examples:

def function(self, box):
    if len(box) == 0:
        for objID in list(self.dict.keys()):
            self.dict[objID] += 1
            if self.dict[objID] > self.maxF:
                self.deleteObject(objID)
        return self.object

This is just a part of the code but I would like to learn how to shorten it and get it to work faster perhaps, but the main point is I would like to learn to write it better.

You can change for objID in list(self.dict.keys()): to for objID in self.dict.keys(): Otherwise this code is fine. One-liners don't necessarily run faster than full loops, and complicated one-liners are hard to understand. — pho
– pho, Commented Oct 18, 2020 at 20:50
@PranavHosangadi. They need to call list because I suspect that self.deleteObject() is deleting the specified object from the dictionary. You can't delete an object from a dictionary at the same time you're iterating over it. Copying the keys is one solution. — Frank Yellin
– Frank Yellin, Commented Oct 18, 2020 at 20:56
And to original poster. I agree with @PranavHosangadi. Your code is nicely laid out and easy to understand. There is nothing to gain here by using map. — Frank Yellin
– Frank Yellin, Commented Oct 18, 2020 at 20:57
You don't transform each object in a list of object (what map is made for) so don't try to use map here — azro
– azro, Commented Oct 18, 2020 at 20:58
Thank you all for the answer, yes @FrankYellin it is deleting object from dictionary so list have to be used. — Marijan Milovec
– Marijan Milovec, Commented Oct 18, 2020 at 20:58

Samwise · Accepted Answer · 2020-10-18 21:34:28Z

3

It's hard to say whether this will work without seeing your deleteObject function, but in general if I were going to modify a regular old dictionary like this I'd use a simple comprehension:

self.dict = {k: v+1 for k, v in self.dict.items() if v <= self.maxF}

(edit per comment) if there's meant to be an invariant where self.object and self.dict must have matching keys, then maybe I'd follow it up with:

self.object = {k: v for k, v in self.object.items() if k in self.dict}

However, if self.dict and self.object must have matching keys, it's a very strong clue that they should not be two different dictionaries in the first place -- instead there should be a single dictionary with compound values (objects, tuples, whatever).

edited Oct 18, 2020 at 21:34

answered Oct 18, 2020 at 21:02

Samwise

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1 Comment

Marijan Milovec Over a year ago

def deleteObject(objID): del self.object[objID] del self.dict[objID]

Rohit Dwivedi · Accepted Answer · 2020-10-18 21:37:46Z

-1

can be approched with MAP as:

map(lambda objID: self.dict[objID] < self.maxF ? self.dict[objID] +=1 : self.deleteObject(objID), self.dict.keys() )

edited Oct 18, 2020 at 21:37

answered Oct 18, 2020 at 21:29

Rohit Dwivedi

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1 Comment

juanpa.arrivillaga Over a year ago

This is not python, python uses ... if condition else .... And jsut write a regular function definition is you are going to assign it to a variable.

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