Optimizing dictionaries in Python -

my question different 1 asked here. asking improvements made code containing dictionaries. however, link explains memory profilers, next step.

i have following 2 sets of code achieve same thing.

first one,

a={1: 'a', 2: 'b', 3: 'c', 4: 'd'} b=[x x in if x in (1,2,3)] b=['a', 'b', 'c'] 

second one,

a={1: 'a', 2: 'b', 3: 'c', 4: 'd'} c=[a[x] x in set(a.keys()) & set([1,2,3])] b=['a', 'b', 'c'] 

i know 1 works better in terms of memory optimized methods, , large sets of data.

thanks in advance!

if you're optimizing memory use generators tool. example:

def get_keys(mapping, keys):     key in keys:         try:             yield mapping[key]         except keyerror:             continue 

on example:

list(get_keys(a, (1, 2, 3))) ['a', 'b', 'c']