Question

I have a list that contains nested lists and I need to know the most efficient way to search within those nested lists.

e.g., if I have

[['a','b','c'],
['d','e','f']]

and I have to search the entire list above, what is the most efficient way to find ‘d’?

Answer 1

Using list comprehension, given:

mylist = [['a','b','c'],['d','e','f']]
'd' in [j for i in mylist for j in i]

yields:

True

and this could also be done with a generator (as shown by @AshwiniChaudhary)

Update based on comment below:

Here is the same list comprehension, but using more descriptive variable names:

'd' in [elem for sublist in mylist for elem in sublist]

The looping constructs in the list comprehension part is equivalent to

for sublist in mylist:
   for elem in sublist

and generates a list that where ‘d’ can be tested against with the in operator.