Delete the dictionary in the list which value is to low

Question

can someone repair my code because it ends after it deletes the first dict. The function should delete all dictionaries which value of density is lower than 5.500

Expected output would be:

[{'name': 'Earth', 'Density': 5.513}]

Mine is:

[{'name': 'Earth', 'Density': 5.513}, 
 {'name': 'Venus', 'Density': 5.204}]`

My code:

base = [
    {"name": "Mars", "Density": 5.427},
    {"name": "Earth", "Density": 5.513},
    {"name": "Venus", "Density": 5.204},
]
density = float(input("density? "))

def deletePlanet(density, base):
    for index in range(0, len(base)):
        while base[index]["Density"] < density:
            del base[index]
            return base

print(deletePlanet(density, base))

Does this answer your question? [Remove dictionary from list](https://stackoverflow.com/questions/1235618/remove-dictionary-from-list) also [How to remove items from a list while iterating?](https://stackoverflow.com/questions/1207406/how-to-remove-items-from-a-list-while-iterating) — Tomerikoo, Dec 10 '20 at 08:20
Also consider changing your list of dicts to a single dict of the form `name: density`. This way it is much easier to remove your wanted items — Tomerikoo, Dec 10 '20 at 08:42

user2390182 · Answer 1 · 2020-12-10T08:52:01.243

4

Only return after the loop:

def deletePlanet(density, base):
    for index in range(0, len(base)):
        if base[index]["Density"] < density:  # why while?
            del base[index]
    return base

This is however bound to fail, as by the time you reach some of the indexes in your loop, they may no longer exist.

But generally you should never repeatedly remove from a list. Build it from scratch for better time complexity:

def deletePlanet(density, base):
    return [d for d in base if d["Density"] >= density]

If you want to mutate the existing list object, use slice assignment:

def deletePlanet(density, base):
    base[:] = [d for d in base if d["Density"] >= density]
    # return base

edited Dec 10 '20 at 08:52

answered Dec 10 '20 at 08:19

user2390182

72,016
6
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IndexError: list index out of range. It dont work( im talking about the first method you mention) – randomobject123 Dec 10 '20 at 08:40
It works only for density from 0 to 5.427. What If i want it to be over this? – randomobject123 Dec 10 '20 at 08:42
@randomobject123 then don't iterate over a list while removing elements from it and use one of the many other ways offered here and in the links above – Tomerikoo Dec 10 '20 at 08:43

score 0 · Answer 2 · answered Dec 10 '20 at 08:20

0

I suggest using

if base[index] < density:

instead of

while base[index] < density:

answered Dec 10 '20 at 08:20

OnlyTrueJames

47
1
8

You all guys just deleting items while iterating them? – adir abargil Dec 10 '20 at 08:36

Sohaib Anwaar · Answer 3 · 2020-12-10T08:30:29.820

0

hy randomobject123! I hope you are doing good. Kindly try this I hope this code will solve your problem.

Code

base = [
    {"name": "Mars", "Density": 5.427},
    {"name": "Earth", "Density": 5.513},
    {"name": "Venus", "Density": 5.204},
]
density = 5.500

def deletePlanet(density, base):
    return [i for i in base if i["Density"] >= density]
    
        

print(deletePlanet(density, base))

Results

[{'name': 'Earth', 'Density': 5.513}]

edited Dec 10 '20 at 08:30

answered Dec 10 '20 at 08:24

Sohaib Anwaar

1,517
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Don't use list-comprehensions for side effects. Also change `density` to `6` and see what happens – Tomerikoo Dec 10 '20 at 08:26
1

I don't think there is some issue while using so! If their is kinldy mention. – Sohaib Anwaar Dec 10 '20 at 08:27
I don't think there is some issue while using so! If their is kinldy mention. – Sohaib Anwaar Dec 10 '20 at 08:27
2

You managed to *not* get rid of the quadratic repeated removal *and* add a spurious in-memory list. This is just bad code. – user2390182 Dec 10 '20 at 08:27
[Is it Pythonic to use list comprehensions for just side effects?](https://stackoverflow.com/questions/5753597/is-it-pythonic-to-use-list-comprehensions-for-just-side-effects) – Tomerikoo Dec 10 '20 at 08:29
Better, but now it's just a copy of another answer =) – user2390182 Dec 10 '20 at 08:32
@schwobaseggl you mean [this one](https://stackoverflow.com/a/1235631/6045800)? ;) – Tomerikoo Dec 10 '20 at 08:40

Delete the dictionary in the list which value is to low

3 Answers3