python, I want to use function in for loop

Question

I want to use sub_code_stop in for loop (in list)

sub_change = [[0, '150', 'aaa'], [0, '151', 'ccc'],
              [0, '152', 'bbb'], [0, '152', 'ddd']]


def sub_code_stop(a):
    for cc in sub_change:
        if a == cc[1]:
            return cc[2]
        else:
            return 0


lis = [['150', '151'], ['152', '153']]
for i in lis:
    print(sub_code_stop(i[0]))

Return is

aaa
0

I want

aaa
bbb

Sayandip Dutta · Accepted Answer · 2019-11-28 05:57:48Z

4

Change the function to:

def sub_code_stop(a):
    for cc in sub_change:
        if a == cc[1]:
            return cc[2]

    return 0

Your previous code was comparing with only the first element of sub_change.

If the second element of each sublist in sub_change were unique, you could do:

sub_change = [[0, '150', 'aaa'], [0, '151', 'ccc'],
              [0, '152', 'bbb'], [0, '153', 'ddd']]
sub_dict = {b:c for _,b,c in sub_change}
lis = [['150', '151'], ['152', '153']]
for i in lis:
    print(sub_dict.get(i[0],0))

edited Nov 28, 2019 at 5:57

answered Oct 21, 2019 at 7:09

Sayandip Dutta

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1 Comment

Se_ung Over a year ago

the original form of sub_change is sub,150,aaa sub,151,bbb sub,152,ccc sub,153,dddd -------------------------------------- sub_code_stop.csv form is sub,150,aaa sub,151,bbb sub,152,ccc sub,153,dddd . . . I want to change row[1] in sub_change to row[2] and allocate it to 2D dictionary like this (first = {'aaa':{'bbb':[]}, 'ccc':{'ddd':[]}}) but the second sub_code_stop('150') return 0

tripleee · Accepted Answer · 2019-10-21 07:16:48Z

2

In your current code if the first element does not match, you leave the function with the return in the else part. You'll have to continue looping to test the next elements.

If you find something you return the appropriate value. If you don't find anything then you have to deal with that after the loop is finished.

def sub_code_stop(a):
    for cc in sub_change:
        if a == cc[1]:
            return cc[2]
    return 0

edited Oct 21, 2019 at 7:16

tripleee

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answered Oct 21, 2019 at 7:12

Matthias

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