TypeError: slice indices must be integers or None or have an __index__ method

TypeError: slice indices must be integers or None or have an __index__ method #

The Python "TypeError: slice indices must be integers or None or have an __index__ method" occurs when we use a non-integer value for slicing (e.g. a float). To solve the error, make sure to use integers when slicing a list, string or any other sequence.

Here is an example of how the error occurs.

Copied!
my_list = ['a', 'b', 'c', 'd']

start = 0.5
stop = 2.5

# ⛔️ TypeError: slice indices must be integers or None or have an __index__ method
result = my_list[start:stop]

We used floats for the start and stop values when slicing the list.

The syntax for list slicing is my_list[start:stop:step].

To solve the error, convert the floating-point values to integers.

Copied!
my_list = ['a', 'b', 'c', 'd']

start = 0.5
stop = 2.5

result = my_list[int(start):int(stop)]

print(result)  # 👉️ ['a', 'b']

We passed the floating-point numbers to the int() class to convert them to integers.

The error often occurs when we use the division operator / because the division operator / always produces a float value

Copied!
print(10/2)  # 👉️ 5.0

Division / of integers yields a float, while floor division // of integers results in an integer.

Copied!
print(10//2)  # 👉️ 5

Once you use integers to slice the sequence, the error will be resolved.

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

Copied!
my_int = 10

print(type(my_int))
print(isinstance(my_int, int))

my_float = 3.14

print(type(my_float))
print(isinstance(my_float, float))

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.

Conclusion #

The Python "TypeError: slice indices must be integers or None or have an __index__ method" occurs when we use a non-integer value for slicing (e.g. a float). To solve the error, make sure to use integers when slicing a list, string or any other sequence.