The error message:
TypeError: unsupported operand type(s) for X: 'type1' and 'type2'
occurs when you try to perform an operation between incompatible data types.
1. Causes and Solutions
Cause 1: Adding a String and an Integer
If you try to add a number (int) and a string (str), Python does not know how to handle it.
Incorrect Code:
age = 25
message = "My age is: " + age # Cannot add str and int
Error Output:
TypeError: can only concatenate str (not "int") to str
Solution: Convert int to str Before Concatenation
message = "My age is: " + str(age) # Correct way
print(message)
Cause 2: Using the Wrong Operator Between Lists, Integers, or Strings
Some operators are not supported between certain types.
Incorrect Code:
result = [1, 2, 3] - [1, 2] # Cannot subtract lists
Error Output:
TypeError: unsupported operand type(s) for -: 'list' and 'list'
Solution: Use set to Subtract Lists
result = list(set([1, 2, 3]) - set([1, 2])) # Returns [3]
Cause 3: Multiplying a List by a Float
Multiplication works between a list and an integer, but not with a float.
Incorrect Code:
nums = [1, 2, 3]
result = nums * 2.5 # Cannot multiply list by float
Error Output:
TypeError: can't multiply sequence by non-int of type 'float'
Solution: Use an Integer
result = nums * 2 # Works fine
print(result) # Output: [1, 2, 3, 1, 2, 3]
Cause 4: Using None in Arithmetic Operations
If a variable is None, you cannot use it in calculations.
Incorrect Code:
x = None
print(x + 5) # Cannot add None and int
Error Output:
TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'
Solution: Assign a Proper Value
x = 0 # Set a valid number
print(x + 5) # Works fine
Cause 5: Incorrect Use of Division (/ vs //)
Python 3 uses floating-point division (/) by default, but integer division (//) works differently.
Incorrect Code:
result = "100" / 5 # Cannot divide string by number
Error Output:
TypeError: unsupported operand type(s) for /: 'str' and 'int'
Solution: Convert the String to an Integer
result = int("100") / 5 # Works fine