How to Parse a String to int or float in Python
Data types play a very major role in any programming language.
They are like the stepping stones of getting introduced to a programming language. They specify the kind of data that a variable can store. Like text or whole numbers or decimals etc.
If you have been programming for a while now, then it is pretty obvious that you must have come across the popular data types like string, int, float, double etc.
In this article, we will discuss about How can we convert a string to a float or int in Python.
Data Types in Python
As mentioned, data types are one of the building blocks of any programming languages, an the same applies to python too.
Python has different data types that can be used to specify a variable about what kind of data it can store. And it is very important that we also know, how to convert from one data type to another data type.
Let’s look at some of the popular data types in python,
String: sample_text = "I am a programmer"
Strings are used to represent text information and are enclosed within single or double quotes.
Int: sample_number = 15
Int is used to represent whole numbers & integers in python.
Float: sample_decimal = 25.5
Float is used to represent decimals and floating-point numbers.
So, now that we have a basic knowledge of the data types, we can now discuss about type-conversion; in simpler words, converting from one data type to another.
We will discuss how to convert a string into whole numbers and floating-point numbers in python.
Let’s get started:
Convert String to Float
In this section we will discuss about how we can convert our string to floating-point numbers.
Using float() method
float() is an inbuilt function in python that allows us to convert any data type into floating-point numbers.
Thus, this is the easiest way to convert a string into floating-point numbers
sample_decimal="25.56"
new_decimal=float(sample_decimal)
print(new_decimal)
print(new_decimal+4.44)
Output:
25.56
30.0
From the above code snippet, we can figure out that after we have converted a string to a float, then we can apply all the basic operations like addition and subtraction to it.
If by mistake instead of a number as a text, we provide some text into the float() function
Example:
sample_text="Convert"
new_decimal=float(sample_text)
print(new_decimal)
Output:
Traceback (most recent call last):
File "<string>", line 2, in <module>
ValueError: could not convert string to float: 'Convert'
Then it will result in an ValueError because the in-built float() is not configured to take alphabets as its parameter.
Using Decimal() method
Since we are only focused on converting strings into floating-point numbers, then we can import the decimal module explicitly and then use the Decimal() method in order to convert the string into a floating-point number.
from decimal import Decimal
sample_decimal="10.55"
new_decimal=Decimal(sample_decimal)
print(new_decimal)
print(new_decimal+9)
Output:
10.55
19.55
But we have got an issue ! If we go on to use a float instead of an int in the last line, then we will un into a error unsupported operand type(s) for *: 'Decimal' and 'float'.
from decimal import Decimal
sample_decimal="10.55"
new_decimal=Decimal(sample_decimal)
print(new_decimal)
print(new_decimal+9.45)
Output:
10.55
Traceback (most recent call last):
File "<string>", line 6, in <module>
TypeError: unsupported operand type(s) for +: 'decimal.Decimal' and 'float'
This happens because the python interpreter doesn’t consider Decimal and float to be at the same level.
How can we fix this issue ?
This is quite easy. We can use the knowledge that we have until now to solve this problem. We can simply typecast the Decimal into float data type using the float() method and then we can use all our operations freely.
Like:
from decimal import Decimal
sample_decimal="10.55"
new_decimal=Decimal(sample_decimal)
print(new_decimal)
print(float(new_decimal)+9.45)
Output:
10.55
20.0
This wraps up our Parsing the string into float section.
We can now discuss about how can we convert a string into int in python in the following section.
Convert String to Int
In a similar way as like of float(), we can use the inbuilt int() method to convert a string to integer/whole number.
Using int() method
int() is an inbuilt function in python that allows us to convert any data type into whole numbers / integers.
Thus, this is the easiest way to convert a string into whole numbers.
sample_number="15"
new_num=int(sample_number)
print(new_num)
print(new_num * 10)
Output:
15
150
However, if we pass any other data like text or hexadecimal number inside a string as a parameter to the int() function, the code will output an ValueError.
sample_number="code"
new_num=int(sample_number)
print(new_num)
Output:
Traceback (most recent call last):
File "<string>", line 3, in <module>
ValueError: invalid literal for int() with base 10: 'code'
Unfortunately, this is the only method that can be used to convert a string into an integer in python.
With this being stated we mark the end of our discussion on how to parse a string as float or int.
Conclusion
In this article we discussed about Data types in python and about typecasting in python.
We discussed how can we convert / parse a string into float or int in python and learnt about the various methods of achieving our desired result.
We also discussed about the possible error cases that we can come across while working with these methods.
I am Dibyanshu Mohanty, Undergraduate Engineering Student at VIT, Vellore with a keen interest in Web and App Development