Convert String to Integer in Python

In this tutorial, we will look at how to convert a string in Python to an integer, int datatype with the help of some examples.

How to convert string to int in Python?

You can use the Python built-in int() function to convert a string to an integer in Python. The following is the syntax –

# convert string s to int
int(s)

It returns the passed string as an integer. Note that if the passed string does not represent a whole number, it will raise an error (even with float numbers represented as string).

Examples

Let’s look at some examples of using the above syntax to convert a string to an integer.

First, let’s apply the int() function on a string containing a whole number, for example, “150”.

# string storing a number
s = "150"
# convert string to int
num = int(s)
# display integer and its type
print(num)
print(type(num))

Output:

150
<class 'int'>

You can see that we get 150 as an integer.

What happens if you pass a floating-point number as a string to the int() function? Let’s find out.

# string storing a floating point number
s = "150.75"
# convert string to int
num = int(s)
# display integer and its type
print(num)
print(type(num))

Output:

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Input In [2], in <module>
      2 s = "150.75"
      3 # convert string to int
----> 4 num = int(s)
      5 # display integer and its type
      6 print(num)

ValueError: invalid literal for int() with base 10: '150.75'

Here we pass “150.75” to the int() function. Since the string passed is not a whole number, we get an error. If you want to convert the above string to a numeric form in Python, use the float() function instead.

# string storing a floating point number
s = "150.75"
# convert string to float
num = float(s)
# display number and its type
print(num)
print(type(num))

Output:

150.75
<class 'float'>

We get the string as a float value.

What happens if you pass a non-numeric string to the int() function? Let’s find out.

# string with text
s = "cat"
# convert string to int
num = int(s)
# display number and its type
print(num)
print(type(num))

Output:

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Input In [4], in <module>
      2 s = "cat"
      3 # convert string to int
----> 4 num = int(s)
      5 # display number and its type
      6 print(num)

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

As expected, we get an error because the passed string cannot be represented as an integer.

You might also be interested in –

1. Extract Numbers From String in Python
2. Python – Check if String Contains Only Numbers
3. Python Tuple to Integer