Python list of dictionaries search

Question

Assume I have this:

[
{\"name\": \"Tom\", \"age\": 10},
{\"name\": \"Mark\", \"age\": 5},
{\"name\": \"Pam\", \"age\": 7}
]

and by searchin

Answer 1

I tested various methods to go through a list of dictionaries and return the dictionaries where key x has a certain value.

Results:

• Speed: list comprehension > generator expression >> normal list iteration >>> filter.
• All scale linear with the number of dicts in the list (10x list size -> 10x time).
• The keys per dictionary does not affect speed significantly for large amounts (thousands) of keys. Please see this graph I calculated: https://imgur.com/a/quQzv (method names see below).

All tests done with Python 3.6.4, W7x64.

from random import randint
from timeit import timeit


list_dicts = []
for _ in range(1000):     # number of dicts in the list
    dict_tmp = {}
    for i in range(10):   # number of keys for each dict
        dict_tmp[f"key{i}"] = randint(0,50)
    list_dicts.append( dict_tmp )



def a():
    # normal iteration over all elements
    for dict_ in list_dicts:
        if dict_["key3"] == 20:
            pass

def b():
    # use 'generator'
    for dict_ in (x for x in list_dicts if x["key3"] == 20):
        pass

def c():
    # use 'list'
    for dict_ in [x for x in list_dicts if x["key3"] == 20]:
        pass

def d():
    # use 'filter'
    for dict_ in filter(lambda x: x['key3'] == 20, list_dicts):
        pass

Results:

1.7303 # normal list iteration 
1.3849 # generator expression 
1.3158 # list comprehension 
7.7848 # filter