Filter List Based On The Element In Nested List At Specific Index

I have a list of list containing: [['4.2','3.4','G'],['2.4','1.2','H'],['8.7','5.4','G']] and i want to obtain the value from the list of list by referring to the alphabet in the

Solution 1:

Simple list comprehension:

L = [['4.2','3.4','G'],['2.4','1.2','H'],['8.7','5.4','G']]
newList = [l[0:2] for l in L if l[2] == 'G']

print(newList)

The output:

[['4.2', '3.4'], ['8.7', '5.4']]

Solution 2:

I would suggest using a collections.defaultdict, as a multi-value dictionary:

from collections import defaultdict
d = defaultdict(list)
for x in L:
    d[x[2]].append(x[:2])

Now you can use d['G'] to get what you wanted, but also d['H'] to get the result for 'H'!

Edit: Source append multiple values for one key in Python dictionary

Solution 3:

There are 2 issues in your code,

1. line = ['4.2', '3.4', 'G'] for 1st iteration
hence to check for'G', look out for line[2] == 'G' instead of line[0][3] == 'G'2. use 'G' instead off 'house'.

>>> for line in L:
... if line[2] == 'G':
...     newList.append([float(i) for i in line[0:2]])
... >>> newList
[[4.2, 3.4], [8.7, 5.4]]

Solution 4:

you can use a dictionary by iterating the list of lists.

lst = [['4.2','3.4','G'],['2.4','1.2','H'],['8.7','5.4','G']]
dict1 = {}

for l in lst:
    if l[2] in dict1.keys():
        dict1[l[2]].append(l[0:2])
    else:
        dict1[l[2]] = [l[0:2]]
        print l[0:2]

print dict1['G']

Solution 5:

A list comprehension will do this:

newList = [[float(j) for j in i[:-1]]for i in L if i[2]=='G']