The Python TypeError is an exception that occurs when the data type of an object in an operation is inappropriate. This can happen when an operation is performed on an object of an incorrect type, or it is not supported for the object. For example, if a string is attempted to be multiplied with an integer, a TypeError is generated.
What Causes TypeError
Some of the most common causes for TypeError in Python are:
- Performing an operation between two incompatible data types e.g. adding a string and an integer.
- Passing an incorrect type to a built-in function e.g. passing a list to the built-in
add()function. - Calling a non-callable object e.g. calling an integer.
- Incorrect list index type e.g. using a string as a list index value instead of an integer.
- Iterating on a non-iterative value e.g. trying to iterate on an integer.
Python TypeError Example
Here’s an example of a Python TypeError thrown when trying to add a string and an integer:
my_integer = 1
my_string = "Hello World"
my_result = my_integer + my_string
In the above example, the string my_string is attempted to be added to an integer my_integer. Since addition cannot be performed between these two types, a TypeError is raised:
File "test.py", line 3, in <module>
my_result = my_integer + my_string
TypeError: unsupported operand type(s) for +: 'int' and 'str'
How to Fix TypeError in Python
To avoid type errors in Python, the type of an object should be checked before performing an operation. This can help ensure that the object type is appropriate for the operation and if the operation is supported by the object.
If the operation is unsupported by the type or if the type is inappropriate for the operation, a message can be displayed to pass the proper type.
Using the above approach, a check can be added to the earlier example:
my_integer = 1
my_string = "Hello World"
if(type(my_integer) != int or type(my_string) != int):
print('One of the variables is not an integer')
else:
my_result = my_integer + my_string
Here, a check is performed to ensure that both variables attempted to be added are integers. If one of them is not an integer, a message is displayed and the error is avoided:
One of the variables is not an integer
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