The TypeError occurs when an operation or function is applied to an object of inappropriate type. This is one of the most common Python errors and indicates a mismatch between expected and actual data types.
# ❌ Problem
result = "5" + 10 # TypeError!
# ✅ Solution: Convert types
result = int("5") + 10 # 15
result = "5" + str(10) # "510"
# ✅ Check types before operations
if isinstance(value, int):
result = value + 10Trying to perform arithmetic operations between strings and numbers.
Trying to call a variable or value as if it were a function.
Passing arguments of the wrong type to a function.
Trying to loop over an object that doesn't support iteration.
Trying to use indexing on objects that don't support it.
age = "25"
next_year = age + 1 # TypeError!
price = 100
message = "Price: " + price # TypeError!# Convert string to int for arithmetic
age = "25"
next_year = int(age) + 1 # 26
# Convert number to string for concatenation
price = 100
message = "Price: " + str(price) # "Price: 100"
# Or use f-strings (recommended)
message = f"Price: {price}" # "Price: 100"
# Or use format()
message = "Price: {}".format(price)number = 42
result = number() # TypeError: 'int' object is not callable
# Common mistake: shadowing built-in functions
list = [1, 2, 3]
new_list = list(range(5)) # TypeError!# Don't add () if it's not a function
number = 42
result = number # Just use the value
# Don't shadow built-in names
my_list = [1, 2, 3] # Use different name
new_list = list(range(5)) # Now works
# If you accidentally shadowed, delete it
del list # Remove the variable
new_list = list(range(5)) # Now worksimport math
result = math.sqrt("16") # TypeError: must be real number, not str
numbers = "1,2,3,4"
total = sum(numbers) # TypeError: unsupported operand typeimport math
result = math.sqrt(16) # Pass number, not string
# Or convert first
result = math.sqrt(int("16"))
numbers = "1,2,3,4"
number_list = [int(x) for x in numbers.split(",")]
total = sum(number_list) # 10count = 5
for i in count: # TypeError: 'int' object is not iterable
print(i)
value = None
for item in value: # TypeError: 'NoneType' object is not iterable
print(item)# Use range() for numbers
count = 5
for i in range(count): # 0, 1, 2, 3, 4
print(i)
# Check if value is iterable
value = None
if value is not None:
for item in value:
print(item)
# Or use default empty list
value = None
for item in value or []:
print(item)number = 12345
first_digit = number[0] # TypeError: 'int' object is not subscriptable
value = None
item = value[0] # TypeError: 'NoneType' object is not subscriptable# Convert to string first
number = 12345
first_digit = str(number)[0] # "1"
# Check before indexing
value = None
if value is not None and len(value) > 0:
item = value[0]TypeError occurs when an operation is applied to an object of inappropriate type, such as adding a string to an integer, calling a non-callable object, or passing wrong argument types to functions.
Convert the operands to compatible types using int(), str(), or float(). For example, convert string to int for arithmetic, or number to string for concatenation.
It means you're trying to call something that isn't a function by adding (). Common causes: calling a variable, shadowing a function name, or using () on a number.
Use type hints, validate input types with isinstance(), use f-strings instead of concatenation, don't shadow built-in names, and use type checkers like mypy.
TypeError means wrong type (e.g., adding string to int). ValueError means right type but invalid value (e.g., int("abc") - string can't be converted to int).
Explore 500+ free tutorials across 20+ languages and frameworks.