How to Resolve Python TypeError: "unsupported operand type(s)"

The TypeError: unsupported operand type(s) is a frequent error in Python. It signals that you've attempted to use an operator (like +, -, *, /) with data types that don't support that specific operation together.

This guide explains the common causes for this error with different type combinations and provides clear solutions.

Understanding "Unsupported Operand Type(s)"

This TypeError fundamentally means you're trying to perform an operation that isn't defined for the combination of data types you're using. For example, you can add two numbers (1 + 2), and you can concatenate two strings ('a' + 'b'), but you can not directly add a number and a string (1 + 'a').

Error: +: int and str

• Cause: Using the addition operator (+) between an integer and a string. Python doesn't know whether you intend mathematical addition or string concatenation.
• Error Example:

  my_int = 10
  my_str = '5'
  try:
      # ⛔️ TypeError: unsupported operand type(s) for +: 'int' and 'str'
      result = my_int + my_str
  except TypeError as e:
      print(e)
• Solutions:
  1. Convert string to number (for addition): Use int() or float().

     result_add = my_int + int(my_str)
     print(f"Addition: {result_add}") # Output: Addition: 15
  2. Convert number to string (for concatenation): Use str().

     result_concat = str(my_int) + my_str
     print(f"Concatenation: {result_concat}") # Output: Concatenation: 105
  3. Use F-strings (for embedding in strings): F-strings handle conversion automatically.

     result_fstring = f"Value: {my_int}{my_str}"
     print(f"F-string: {result_fstring}") # Output: f-string: Value: 105
• Note: The input() function always returns a string. Convert its result using int() or float() if numeric operations are needed.

Error: -: str and str

• Cause: Using the subtraction operator (-) with two strings. Subtraction is not defined for strings.
• Error Example:

  str_1 = '50'
  str_2 = '20'
  try:
      # ⛔️ TypeError: unsupported operand type(s) for -: 'str' and 'str'
      result = str_1 - str_2
  except TypeError as e:
      print(e)
• Solution: Convert both strings to numbers (int or float) before subtracting.

  result = int(str_1) - int(str_2)
  print(result) # Output: 30

Error: -: int and function

• Cause: Attempting to subtract a function object itself (instead of its return value) from an integer.
• Error Example:

  def get_num():
      return 25
  try:
      # ⛔️ TypeError: unsupported operand type(s) for -: 'int' and 'function'
      result = 50 - get_num # Forgot parentheses ()
  except TypeError as e:
      print(e)
• Solution: Call the function using parentheses () to get its return value before performing the subtraction.

  result = 50 - get_num() # Call the function
  print(result)           # Output: 25
• Ensure the function actually returns a numeric value compatible with subtraction.

Error: /: list and int

• Cause: Trying to use the division operator (/) between a list object and an integer. Division isn't defined for lists.
• Error Example:

  my_list = [10, 20, 30]
  my_int = 5
  try:
      # ⛔️ TypeError: unsupported operand type(s) for /: 'list' and 'int'
      result = my_list / my_int
  except TypeError as e:
      print(e)
• Solutions:
  1. Divide a specific element: Access an element by index.

     result = my_list[0] / my_int
     print(result) # Output: 2.0
  2. Divide each element: Use a loop or list comprehension.

     new_list = [num / my_int for num in my_list]
     print(new_list) # Output: [2.0, 4.0, 6.0]
  3. Divide the sum: Use sum().

     result = sum(my_list) / my_int
     print(result) # Output: 12.0

Error: /: tuple and int

• Cause: Similar to lists, trying to use the division operator (/) between a tuple object and an integer.
• Error Example:

  my_tuple = (10, 20, 30) # Or my_tuple = 10, 20, 30
  my_int = 2
  try:
      # ⛔️ TypeError: unsupported operand type(s) for /: 'tuple' and 'int'
      result = my_tuple / my_int
  except TypeError as e:
      print(e)
• Solutions: The solutions are analogous to lists (access element, iterate, sum).
  1. Divide a specific element:

     result = my_tuple[0] / my_int
     print(result) # Output: 5.0
  2. Divide each element:

     new_list = [x / my_int for x in my_tuple]
     new_tuple = tuple(new_list)
     print(new_tuple) # Output: (5.0, 10.0, 15.0)
  3. Divide the sum:

     result = sum(my_tuple) / my_int
     print(result) # Output: 30.0

Error: /: str and int

• Cause: Trying to use the division operator (/) between a string and an integer.
• Error Example:

  my_str = '10'
  my_num = 5
  try:
      # ⛔️ TypeError: unsupported operand type(s) for /: 'str' and 'int'
      result = my_str / my_num
  except TypeError as e:
      print(e)
• Solution: Convert the string to a number (int or float) before dividing.

  result = int(my_str) / my_num
  print(result) # Output: 2.0
• Use // for floor division if an integer result is desired (after conversion).

Error: *: float and decimal.Decimal

• Cause: Using arithmetic operators between standard Python floats and decimal.Decimal objects. These types have different internal representations and precision rules, making direct operations ambiguous.
• Error Example:

  from decimal import Decimal
  my_float = 3.2
  my_decimal = Decimal('3.14')
  try:
      # ⛔️ TypeError: unsupported operand type(s) for *: 'float' and 'decimal.Decimal'
      result = my_float * my_decimal
  except TypeError as e:
      print(e)
• Solution: Convert one type to match the other. Converting the float to Decimal is generally preferred for maintaining precision.

  from decimal import Decimal
  my_float = 3.2
  my_decimal = Decimal('3.14')
  
  # Convert float to Decimal
  result = Decimal(my_float) * my_decimal
  print(result) # Output: 10.04800000000000055777604757
  
  # Or convert Decimal to float (potential precision loss)
  # result = my_float * float(my_decimal)
  # print(result) # Output: 10.048

General Debugging: Checking Variable Types

If you encounter an "unsupported operand type(s)" error and aren't sure why, check the types of your variables using type() or isinstance():

my_var1 = 10
my_var2 = "5"

print(f"my_var1: value={my_var1}, type={type(my_var1)}")
print(f"my_var2: value={my_var2}, type={type(my_var2)}")
print(f"Is my_var1 an int? {isinstance(my_var1, int)}")
print(f"Is my_var2 a str? {isinstance(my_var2, str)}")

This helps identify the incompatible types involved in the operation.

Conclusion

The TypeError: unsupported operand type(s) error highlights the importance of understanding data types and operator compatibility in Python.

• The solution usually involves converting one or both operands to compatible types (often using int(), float(), str(), or Decimal()) or ensuring you are operating on the intended data (e.g., calling a function instead of using the function object itself, or accessing elements within a list/tuple).
• Checking variable types can be a valuable debugging step.