TypeError: 'in <string>' requires string as left operand, not list

TypeError: 'in <string>' requires string as left operand, not list #

The Python "TypeError: 'in <string>' requires string as left operand, not list" occurs when we use the in operator with a left-hand side value of a list and a right-hand side value of a string. To solve the error, move the list to the right-hand side of the in operator.

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my_str = 'bob'

my_list = ['alice', 'bob', 'carl']

# ⛔️ TypeError: 'in <string>' requires string as left operand, not list
result = my_list in my_str

We used the in operator with a list on the left-hand side and a string on the right-hand side which caused the error.

To solve the error, move the list to the right-hand side of the in operator.

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my_str = 'bob'

my_list = ['alice', 'bob', 'carl']

result = my_str in my_list
print(result)  # 👉️ True

if my_str in my_list:
    print('string is in list')
else:
    print('string is NOT in list')

The in operator tests for membership. For example, x in l evaluates to True if x is a member of l, otherwise it evaluates to False.

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my_list = ['alice', 'bob', 'carl']

print('bob' in my_list)  # 👉️ True

print('james' in my_list)  # 👉️ False

If you need to check if a string is NOT in a list, use the not in operator instead.

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my_list = ['alice', 'bob', 'carl']

print('bob' not in my_list)  # 👉️ False

print('james' not in my_list)  # 👉️ True

x not in l returns the negation of x in l.

You can also use this approach to check if a list contains another list, if you have a two-dimensional list.

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my_list = [['alice'], ['bob'], ['carl']]

print(['bob'] in my_list)  # 👉️ True

print(['alice'] in my_list)  # 👉️ True

print(['james'] in my_list)  # 👉️ False