Learn how to convert values between different types in Python using built-in functions.

Type Conversion

Sometimes you have a value of one type but you need it in another. A number stored as a string that you want to do math with. A float you want to round down to an integer. Python gives you built-in functions to convert between types — this is called type conversion.

There are two kinds:

Explicit conversion — you convert it yourself using a function like int(), str(), float()
Implicit conversion — Python converts it automatically behind the scenes

Explicit conversion

int() — convert to integer

Converts a value to a whole number.

# string to int
age = int("22")
print(age)          # 22
print(type(age))    # <class 'int'>

# float to int — drops the decimal, does NOT round
x = int(9.99)
print(x)            # 9

# bool to int
print(int(True))    # 1
print(int(False))   # 0

int() drops the decimal — it does not round. int(9.99) gives you 9, not 10. If you want rounding, use round() instead.

You cannot convert a string that contains a decimal or letters:

int("3.14")    # ValueError — use float() first
int("hello")   # ValueError — cannot convert text to a number

float() — convert to float

Converts a value to a decimal number.

# string to float
price = float("9.99")
print(price)         # 9.99
print(type(price))   # <class 'float'>

# int to float
x = float(5)
print(x)             # 5.0

# bool to float
print(float(True))   # 1.0
print(float(False))  # 0.0

Unlike int(), float() can handle strings with decimal points:

print(float("3.14"))   # 3.14
print(float("10"))     # 10.0 — works too

str() — convert to string

Converts any value to a string. This one almost never fails.

age = 22
price = 9.99
is_active = True

print(str(age))        # "22"
print(str(price))      # "9.99"
print(str(is_active))  # "True"
print(str(None))       # "None"

You will use str() most often when you want to join a number into a string using +:

age = 22

# This breaks — cannot add int to str
print("I am " + age)           # TypeError

# This works — convert first
print("I am " + str(age))      # I am 22

In practice, f-strings are cleaner than using str() with concatenation. f"I am {age}" is easier to read than "I am " + str(age). Use str() when you specifically need a string variable, not just for printing.

bool() — convert to boolean

Converts a value to True or False. This one is important to understand well because Python uses it constantly in conditions.

print(bool(1))        # True
print(bool(0))        # False
print(bool("hello"))  # True
print(bool(""))       # False
print(bool([1, 2]))   # True
print(bool([]))       # False
print(bool(None))     # False

The rule is simple — these values are always False:

Value	Type
`0`	int
`0.0`	float
`""`	empty string
`[]`	empty list
`{}`	empty dict
`()`	empty tuple
`None`	NoneType

Everything else is True. These are called falsy and truthy values, and Python uses them in if statements automatically:

name = ""

if name:
    print(f"Hello, {name}!")
else:
    print("No name provided.")
# No name provided.

Python called bool(name) behind the scenes. Because name is an empty string, it is falsy — so the else branch ran.

Implicit conversion

Python sometimes converts types automatically when it makes obvious sense — you do not ask for it, it just happens.

# int + float — Python promotes int to float automatically
result = 5 + 2.0
print(result)         # 7.0
print(type(result))   # <class 'float'>

Python will not do implicit conversion when it could cause confusion or data loss:

# str + int — Python refuses, raises TypeError
print("Age: " + 25)   # TypeError: can only concatenate str (not "int") to str

This is intentional. Python does not guess — if there is ambiguity, it raises an error and makes you be explicit.

Conversion between types — what works

Not every conversion is valid. Here is a clear map:

From	To `int`	To `float`	To `str`	To `bool`
`int`	—	✅	✅	✅
`float`	✅ (drops decimal)	—	✅	✅
`str`	✅ (if numeric)	✅ (if numeric)	—	✅
`bool`	✅	✅	✅	—
`None`	❌	❌	✅	✅

A practical example

A common real-world pattern — getting a number from input() and doing math with it:

raw = input("Enter a price: ")       # always returns str
price = float(raw)                   # convert to float
discounted = price * 0.9             # apply 10% discount

print(f"Original: {price}")
print(f"Discounted: {discounted:.2f}")

Output:

Enter a price: 50
Original: 50.0
Discounted: 45.00

Summary

Function	Converts to	Fails when
`int(x)`	Whole number	String has decimals or letters
`float(x)`	Decimal number	String has letters
`str(x)`	String	Almost never
`bool(x)`	True or False	Almost never

Type Conversion

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