Question

I am have two lists:

a= [['A', 'B', 'C', 3], ['P', 'Q', 'R', 4]]

b=[['K',1,1,1,1,1], ['L',1,1,1,1,1], ['M', 1,1,0,1,1], ['J', 0,0,0,0,0], ['A', 0,0,0,1,1], ['P',0,1,0,1,1 ]]

I want the output like:

Output=[['A', 0,0,0,1,1], ['P',0,1,0,1,1 ]]

I am trying to search the a in b using the a[idx][0]. Then I want to collect those items and would like the Output something like above.

My code looks like:

Output=[]
for idx in range(len(Test)):
    a_idx = [y[0] for y in b].index(a[idx][0])
    a_in_b = b[a_idx]
    Output.append(a_in_b[:])

print Output 

This does not give me the desired output. Can someone please help?

Answer 1

While eumiro’s answer is a better one, you asked for a version which uses index. My version seems to work consistently:

a= [['A', 'B', 'C', 3], ['P', 'Q', 'R', 4]]
b=[['K',1,1,1,1,1], ['L',1,1,1,1,1], ['M', 1,1,0,1,1], ['J', 0,0,0,0,0], ['A', 0,0,0,1,1], ['P',0,1,0,1,1 ]]
src = [y[0] for y in b]; # I moved this out here so that it is only calculated once
Output = []
for i in range(len(a)):  # You have Test here instead??? Not sure why
     ai  = src.index( a[ i ][ 0 ] )
     Output.append( b[ ai ][:] )