Watch Now This tutorial has a related video course created by the Real Python team. Watch it together with the written tutorial to deepen your understanding: **Convert a Python String to int**

Integers are whole numbers. In other words, they have no fractional component. Two data types you can use to store an integer in Python are `int`

and `str`

. These types offer flexibility for working with integers in different circumstances. In this tutorial, you’ll learn how you can convert a Python string to an `int`

. You’ll also learn how to convert an `int`

to a string.

By the end of this tutorial, you’ll understand:

- How to store integers using
`str`

and`int`

- How to convert a Python string to an
`int`

- How to convert a Python
`int`

to a string

Let’s get started!

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## Representing Integers in Python

An integer can be stored using different types. Two possible Python data types for representing an integer are:

For example, you can represent an integer using a string literal:

```
>>> s = "110"
```

Here, Python understands you to mean that you want to store the integer `110`

as a string. You can do the same with the integer data type:

```
>>> i = 110
```

It’s important to consider what you specifically mean by `"110"`

and `110`

in the examples above. As a human who has used the decimal number system for your whole life, it may be obvious that you mean the number *one hundred and ten*. However, there are several other number systems, such as **binary** and **hexadecimal**, which use different bases to represent an integer.

For example, you can represent the number *one hundred and ten* in binary and hexadecimal as *1101110* and *6e* respectively.

You can also represent your integers with other number systems in Python using the `str`

and `int`

data types:

```
>>> binary = 0b1010
>>> hexadecimal = "0xa"
```

Notice that `binary`

and `hexadecimal`

use prefixes to identify the number system. All integer prefixes are in the form `0?`

, in which you replace `?`

with a character that refers to the number system:

**b:**binary (base 2)**o:**octal (base 8)**d:**decimal (base 10)**x:**hexadecimal (base 16)

**Technical Detail:** The prefix is not required in either an integer or string representation when it can be inferred.

`int`

assumes the literal integer to be **decimal**:

```
>>> decimal = 303
>>> hexadecimal_with_prefix = 0x12F
>>> hexadecimal_no_prefix = 12F
File "<stdin>", line 1
hexadecimal_no_prefix = 12F
^
SyntaxError: invalid syntax
```

The string representation of an integer is more flexible because a string holds arbitrary text data:

```
>>> decimal = "303"
>>> hexadecimal_with_prefix = "0x12F"
>>> hexadecimal_no_prefix = "12F"
```

Each of these strings represent the same integer.

Now that you have some foundational knowledge about how to represent integers using `str`

and `int`

, you’ll learn how to convert a Python string to an `int`

.

## Converting a Python String to an `int`

If you have a decimal integer represented as a string and you want to convert the Python string to an `int`

, then you just pass the string to `int()`

, which returns a decimal integer:

```
>>> int("10")
10
>>> type(int("10"))
<class 'int'>
```

By default, `int()`

assumes that the string argument represents a decimal integer. If, however, you pass a hexadecimal string to `int()`

, then you’ll see a `ValueError`

:

```
>>> int("0x12F")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '0x12F'
```

The error message says that the string is not a valid decimal integer.

**Note:**

It’s important to recognize the difference between two types of failed results of passing a string to `int()`

:

**Syntax Error:**A`ValueError`

will occur when`int()`

doesn’t know how to parse the string using the provided base (10 by default).**Logical Error:**`int()`

does know how to parse the string, but not the way you expected.

Here’s an example of a logical error:

```
>>> binary = "11010010"
>>> int(binary) # Using the default base of 10, instead of 2
11010010
```

In this example, you meant for the result to be *210*, which is the decimal representation of the binary string. Unfortunately, because you didn’t specify that behavior, `int()`

assumed that the string was a decimal integer.

One good safeguard for this behavior is to always define your string representations using explicit bases:

```
>>> int("0b11010010")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '0b11010010'
```

Here, you get a `ValueError`

because `int()`

doesn’t know how to parse the binary string as a decimal integer.

When you pass a string to `int()`

, you can specify the number system that you’re using to represent the integer. The way to specify the number system is to use `base`

:

```
>>> int("0x12F", base=16)
303
```

Now, `int()`

understands you are passing a hexadecimal string and expecting a decimal integer.

**Technical Detail:** The argument that you pass to `base`

is not limited to 2, 8, 10, and 16:

```
>>> int("10", base=3)
3
```

Great! Now that you’re comfortable with the ins and outs of converting a Python string to an `int`

, you’ll learn how to do the inverse operation.

## Converting a Python `int`

to a String

In Python, you can convert a Python `int`

to a string using `str()`

:

```
>>> str(10)
'10'
>>> type(str(10))
<class 'str'>
```

By default, `str()`

behaves like `int()`

in that it results in a decimal representation:

```
>>> str(0b11010010)
'210'
```

In this example, `str()`

is smart enough to interpret the binary literal and convert it to a decimal string.

If you want a string to represent an integer in another number system, then you use a formatted string, such as an f-string (in Python 3.6+), and an option that specifies the base:

```
>>> octal = 0o1073
>>> f"{octal}" # Decimal
'571'
>>> f"{octal:x}" # Hexadecimal
'23b'
>>> f"{octal:b}" # Binary
'1000111011'
```

`str`

is a flexible way to represent an integer in a variety of different number systems.

## Conclusion

Congratulations! You’ve learned so much about integers and how to represent and convert them between Python string and `int`

data types.

In this tutorial, you learned:

- How to use
`str`

and`int`

to store integers - How to specify an explicit number system for an integer representation
- How to convert a Python string to an
`int`

- How to convert a Python
`int`

to a string

Now that you know so much about `str`

and `int`

, you can learn more about representing numerical types using `float()`

, `hex()`

, `oct()`

, and `bin()`

!

Watch Now This tutorial has a related video course created by the Real Python team. Watch it together with the written tutorial to deepen your understanding: **Convert a Python String to int**