Finding a certain item in a list of lists in Python -

i learning python , need advice regarding searching items in list. have list contains list of lists. how can search item in list , return value same list example below.

example:  mylist = [['red', 'tomato'], ['green', 'pear'], ['red', 'strawberry'], ['yellow', 'lemon']]  word = 'green' return pear 

is possible find first instance or n-th instance in list well?

first_instance = 'red' return tomato  last_instance = 'red' return strawberry 

you can use collections.defaultdict:

using once dictionary created it'll take o(1) lookup find instance of "red" or other color.

>>> mylist = [['red', 'tomato'], ['green', 'pear'], ['red', 'strawberry'], ['yellow', 'lemon']] >>> collections import defaultdict >>> dic = defaultdict(list) >>> k,v in mylist:     dic[k].append(v) ...      >>> dic['red'][0] #first instance 'tomato' >>> dic['red'][-1] #last instance 'strawberry' >>> dic["yellow"][0] #first instance of yellow 'lemon' 

define simple function here handle index errors:

>>> def solve(n, color, dic):     try:         return dic[color][n]     except indexerror:         return "error: {0} has {1} instances".format(color,len(dic[color])) ...      >>> dic = defaultdict(list) >>> k,v in mylist:     dic[k].append(v) ...      >>> solve(0, "red", dic) 'tomato' >>> solve(-1, "red", dic) 'strawberry' >>> solve(0, "yellow", dic) 'lemon' >>> solve(1, "yellow", dic) 'error: yellow has 1 instances'