Converting string to int in Python is easy using the built-in `int()`

function.

For example, let’s convert the string “**100**” to an integer:

num_str = "100" num_int = int(num_str)

## How to Convert Comma-Separated Number String to Int?

To convert a comma-separated number string (e.g. `1,000,000`

) to an int in Python, first, get rid of the commas with the `replace()`

method. Then convert the result to an int using the `int()`

function:

big_num_str = "80,129,553" big_num_int = int(big_num_str.replace(",", "")) print(big_num_int)

Output:

80129553

## How to Convert Number Strings in Different Bases

Using `int()`

to convert a string to an integer assumes that a string represents a **decimal integer** (a 10-base number).

### String to Int in Different Base Systems

If you pass for example a hexadecimal string into the `int()`

function, you see an error:

int("0x6F")

Outcome:

ValueError: invalid literal for int() with base 10: '0x6F'

This `ValueError`

says that the string you tried to convert is not a valid decimal integer.

There is an easy way to fix this problem.

When you use the `int()`

function to convert a string to an int, you can specify the number system as the second argument. This happens with the `base`

attribute.

To convert a hexadecimal string to an int, let the `int()`

function know you’re dealing with a 16-base system:

int("0x6F", base=16) # '111'

You now know how to convert a string into an integer in Python. To make it complete, let’s turn things around and convert integers back to strings.

## How to Convert Ints to Strings in Python

You can convert an integer to a string using the built-in `str()`

function.

num_int = 100 str(100) # '100'

This is the basic use case. But if you are dealing with other numeric systems, read along.

The `str()`

function is clever enough to tell that a binary literal is passed into it. For example, let’s convert a binary integer `0011`

to a string that represents a regular integer:

bin = 0b0011 str(bin) # '3'

But if you want to represent an integer as a string in another number system, use the f-string formatting.

The number systems into which you can convert an integer are binary, hexadecimal, and octal.

Examples:

num = 100 num_binary_str = f"{num:b}" # '1100100' num_hexadecimal_str = f"{num:x}" # '64' num_octal_str = f"{num:o}" # '144'

## Conclusion

Converting string to int in Python is easy with the built-in `int()`

function:

int("300") # 300

To convert an integer to a string, use the built-in `str()`

function.

str(23) # '23'

Thanks for reading. I hope you find it useful. Happy coding!