CODEWITHSUNDEEP
pythonlistdictionaryiteration
German Sabio
German Sabio

Reputation: 21

Is there a more efficient way to iterate over a list of dictionaries?

I'm trying to iterate over a list of dictionaries and keeping only those with a year value in their yearID key. Essentially, the list (statistics) is baseball statistics and each row (dictionary) are the stats of a player during a year.

This code seems to work just fine (for VERY small lists of dictionaries), but as soon as the size of the list goes over 40 or 50, Thonny crushes:

def filter_by_year(statistics, year, yearid):

    nlist = []
    for dicts in statistics:
        if str(dicts[yearid]) == str(year):
            nlist.append(dicts)

    return nlist

Upvotes: 2

Views: 1264

Answers (5)

DYZ
DYZ

Reputation: 57033

Of all the methods presented so far (by prashant rana, Zaid Afzal, alec_a, and Steven Burnap), yours - the original one - is the most efficient. It becomes somewhat 3x faster if you eliminate the unnecessary conversion to the strings:

def filter_by_year(statistics, year, yearid): 
    nlist = [] 
    for dicts in statistics: 
        if dicts[yearid] == year: 
            nlist.append(dicts) 
    return nlist

Upvotes: 2

sahasrara62
sahasrara62

Reputation: 11228

A filter can also be a good way

def filter_by_year(statistics, year, yearid):
    nlist = list(filter (lambda dicts: str(dicts[yearid]) == str(year), statistics))
    return nlist

Upvotes: 0

Zaid Afzal
Zaid Afzal

Reputation: 356

You could use a generator to only grab year and keep index of dictionary being iterated.

def filter_by_year(statistics, year, yearid):

    nlist = []

    for i, yearid_ in enumerate(dict[yearid] for dict in statistics): 
        if str(yearid_) == str(year):
            nlist.append(statistics[i])

    return nlist

Upvotes: 0

Alec
Alec

Reputation: 9536

Depends what you mean by "efficient." Your code should work fine for large amounts of dictionaries, so I'm gonna assume you mean efficient in terms of code written.

In that case, nlist can be simplified into a simple list comprehension:

[dicts for dicts in statistics if str(dicts[yearid]) == str(year)]

Upvotes: 2

user1342784
user1342784

Reputation:

I have no idea if it's more efficient, but a list comprehension is cleaner code:

return [dicts for dicts in statistics if str(dicts[yearid]) == str(year)]

Upvotes: 1

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