TypeError: can only concatenate tuple (not "list") to tuple

TypeError: can only concatenate tuple (not "list") to tuple #

The Python "TypeError: can only concatenate tuple (not "list") to tuple" occurs when we try to concatenate a tuple and a list. To solve the error, make sure the two values are of type list or of type tuple before concatenating them.

Here is an example of how the error occurs.

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my_tuple = ('a', 'b')
my_list = ['c', 'd']

# ⛔️ TypeError: can only concatenate tuple (not "list") to tuple
result = my_tuple + my_list

We tried to use the addition (+) operator to concatenate a tuple and a list which caused the error.

If you meant to concatenate two tuples, declare a tuple instead of a list, or convert the list to a tuple.

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my_tuple = ('a', 'b')
my_list = ['c', 'd']

result = my_tuple + tuple(my_list)

print(result)  # 👉️ ('a', 'b', 'c', 'd')

We converted the list to a tuple and concatenated the two tuples.

Conversely, you can convert the tuple into a list and concatenate the two lists.

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my_tuple = ('a', 'b')
my_list = ['c', 'd']

result = list(my_tuple) + my_list

print(result)  # 👉️ ['a', 'b', 'c', 'd']

If you declared the tuple by mistake, tuples are constructed in the following ways:

• Using a pair of parenthesis () creates an empty tuple
• Using a trailing comma - a, or (a,)
• Separating items with commas - a, b or (a, b)
• Using the tuple() constructor

If you meant to append the tuple to a list, use the append() method.

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my_tuple = ('c', 'd')
my_list = [('a', 'b')]

my_list.append(my_tuple)
print(my_list)  # 👉️ [('a', 'b'), ('c', 'd')]

The list.append() method adds an item to the end of the list.

The method returns None as it mutates the original list.

If you aren't sure what type a variable stores, use the built-in type() class.

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my_tuple = ('a', 'b')
print(type(my_tuple))  # 👉️ <class 'tuple'>
print(isinstance(my_tuple, tuple))  # 👉️ True

my_list = ['c', 'd']
print(type(my_list))  # 👉️ <class 'list'>
print(isinstance(my_list, list))  # 👉️ True

The type class returns the type of an object.

The isinstance function returns True if the passed in object is an instance or a subclass of the passed in class.