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Type conversion means changing a value from one data type to another.
For example:
Here, age is a string.
If we want to perform calculations with it, we can convert it into an integer:
Now age contains an integer:
Python provides several built-in functions for conversion:
Suppose a user enters their age:
Even if the user enters:
Python stores the input as:
It is a string, not an integer.
We can verify this:
If the user enters 25, the output is:
If we want to perform mathematical operations, we need to convert it:
If the user enters:
the output is:
input() always returns the user's input as a str.Python conversions can generally be understood in two ways:
Python performs the conversion automatically in certain situations.
Python produces:
You tell Python to convert the value.
The result is:
Python can automatically convert between some numeric types during an operation.
For example:
Here:
Python handles the numeric conversion automatically.
Output:
The result is a float.
You do not need to manually write:
for this simple numeric operation.
Python handles the conversion for you.
floatThere is another important rule.
In Python 3, / performs true division and returns a float.
Example:
Output:
Even though both numbers are integers, the result is a float.
Compare:
with:
Results:
We will study // in more detail when we learn Python operators.
Explicit conversion means that you manually tell Python which type you want.
The most common functions are:
Let's learn each one.
int()Suppose we have:
Currently:
Convert it using:
Now:
Example:
Output:
float()Suppose:
This is a string.
Convert it:
Now it becomes:
Example:
Output:
You can convert an integer into a float:
Output:
So:
You can also convert a float to an integer:
Output:
int() does not round the number.
It removes the decimal portion.
For example:
Output:
So int() truncates toward zero.
not:
Use str() when you want a string representation of a value.
Example:
Output:
Without str():
Python raises a TypeError because you cannot directly concatenate a string and an integer using +.
Usually, an f-string is even cleaner:
Output:
bool()The bool() function converts a value to either:
or:
Examples:
Output:
For strings:
Output:
The basic idea is:
We call these truthy and falsy values.
Python allows almost any object to be tested in an if condition.
For example:
Output:
Why?
Because "Sumit" is a non-empty string, so it is truthy.
The following values are commonly important to remember as falsy:
For example:
Output:
Look at this:
The result is:
Why?
Because "False" is a non-empty string.
Python does not read the text "False" and automatically turn it into the Boolean value False.
Compare:
with:
Results:
The second one is a string containing characters.
These are all truthy:
Why?
Because:
"0" is a non-empty string"False" is a non-empty string" " contains a space[0] contains one item[False] contains one item100 is not zero-10 is not zeroOutput:
But:
Output:
Even a single space makes the string non-empty.
One common beginner mistake is:
This raises:
Why?
Because "499.99" is not a valid integer string.
Python can directly convert:
but not:
If the string contains a decimal number:
Output:
So the conversion happens in two steps:
ValueError?A ValueError occurs when Python receives a value of the correct general type but the value itself is not suitable for the requested operation.
For example:
Python cannot turn "hello" into an integer.
So it raises:
Another example:
This also causes a ValueError.
This is one of the most important practical uses of type conversion.
Suppose we ask the user for quantity:
If the user enters:
Python receives:
To calculate with it:
If the user enters:
the output is:
For prices, use float() when appropriate:
Example input:
Output:
This pattern is extremely common in real Python programs.
Instead of writing:
you can write:
If name is empty:
the condition is false.
If it contains text:
the condition is true.
This makes Python code shorter and easier to read.
Suppose:
Instead of:
you can write:
This is a common Python style.
If the cart contains items:
then:
Output:
| Type | Example | Who performs conversion? |
|---|---|---|
| Implicit | 5 + 2.5 | Python |
| Explicit | int("25") | Programmer |
| Explicit | float("9.5") | Programmer |
| Explicit | str(100) | Programmer |
| Explicit | bool(0) | Programmer |
| Situation | Don't | Do |
|---|---|---|
| User enters quantity | qty = input() and calculate directly | qty = int(input()) |
| Decimal input | int("75.50") | float("75.50") |
| Float to int | Expect rounding | Remember int() truncates |
| Number + text | "Age: " + age | "Age: " + str(age) or an f-string |
| Empty list check | len(items) == 0 everywhere | if not items: |
| Boolean string | Assume "False" means False | Remember any non-empty string is truthy |
| Invalid conversion | Ignore possible ValueError | Validate or handle the error |
int(4.85) return?int("35.75")?input() return?False?100 / 20 in Python 3?bool("False") return True?Create a small billing program that receives product information as strings and converts the values into the correct data types.
In this lesson, you learned:
int() worksfloat() worksstr() worksbool() worksinput() returns a stringint("35.75") raises ValueErrorbool("False") is Trueif statementsIn the next lesson, we will continue your Python learning journey with Checking Data Types (isinstance) (3: Data Types).
👉 Continue to Next Lesson: Checking Data Types (isinstance) →
Continue learning with hands-on practice, examples, and exercises in the upcoming topic.
| Previous Lesson | Next Lesson |
|---|---|
| Data Types Overview | Checking Data Types (isinstance) |
Test your understanding of this lesson with 6 questions. Each question has one correct answer.