Python check if Items are in list

Question

I am trying to iterate through two lists and check if items in list_1 are in list_2. If the item in list_1 is in list_2 I would like to print the item in list_2. If the item is NOT in list_2 I would like print the item from list_1. The below code accomplishes this partially but because I am performing two for loops I am getting duplicate values of list_1. Can you please direct me in a Pythonic way to accomplish?

list_1 = ['A', 'B', 'C', 'D', 'Y', 'Z']
list_2 = ['Letter A',
          'Letter C',
          'Letter D',
          'Letter H',
          'Letter I',
          'Letter Z']

for i in list_1:
    for x in list_2:
        if i in x:
            print(x)
        else:
            print(i)

Current Output:

Letter A
A
A
A
A
A
B
B
B
B
B
B
C
Letter C
C
C
C
C
D
D
Letter D
D
D
D
Y
Y
Y
Y
Y
Y
Z
Z
Z
Z
Z
Letter Z

Desired Output:

Letter A
B
Letter C
Letter D
Y
Letter Z

Asked By: MBasith

||

Source

Answer 1

You can write:

for i in list_1:
    found = False
    for x in list_2:
        if i in x:
            found = True
            break
    if found:
        print(x)
    else:
        print(i)

The approach above ensure that you either print x or i and we only print one value per element in list_1.

You could also write (which is the same thing as above but makes use of the ability to add an else to a for loop):

for i in list_1:
    for x in list_2:
        if i in x:
            print(x)
            break
    else:
        print(i)

Answered By: Simeon Visser

Answer 2

for i in range(len(list_1)):
  if list_1[i] in list_2[i]:
    print(list_2[i])
  else:
    print(list_1[i])

Answered By: Moe

Answer 3

for i in list_1:
    found = False
    for x in list_2:
        if i in x:
            found = True
            print(x)
    if found == False:
        print(i)

Answered By: shamssss.169

Answer 4

Oneliner:

[print(i) for i in ["Letter {}".format(i) if "Letter {}".format(i) in list_2 else i for i in list_1]]

Outputs:

Letter A
B
Letter C
Letter D
Y
Letter Z

Answered By: Anton vBR

Answer 5

for i in list_1:
    for x in list_2:
        if i not in x:
            continue
        else:
            print(x)

Answered By: F.Alwan

Python check if Items are in list

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