Tutorial: How to Convert String to Float in Python

How to Convert String to Float in Python


As a Python programmer, dealing with data is a crucial aspect of your day-to-day work. However, as much as we strive to ensure the consistency and accuracy of our data sets, mishaps can occur when working with strings that must be converted to floats for further computation.

The process of converting strings to floats may seem simple enough at first glance; however, it requires careful consideration and attention in practice. This blog post will provide an overview of why converting strings to floats is essential in Python programming and give you practical insights into how you can go about it efficiently. Whether you’re a beginner or an experienced developer looking to brush up on your skills, this article will contain valuable information for all levels. Read on and discover everything you need to know about converting strings to floats in Python.

Table of Contents:

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What is a float?

In Python, a float is a data type that represents real numbers with floating-point precision. It’s used to store decimal values such as 3.14, 0.1234, or -1.23456.

How are floats different from integers?

Floats differ from integers in that they can represent fractional values while integers cannot. Integers only represent whole numbers without any fractional parts like 5 and -17.

Additionally, floats consume more memory than integers due to their higher precision level and the need for an additional sign bit and exponent.

Here’s an example of how you can create a variable with the float data type:

my_float = 2.71828

#This will output: 


The value of my_float is assigned using the decimal point which signifies it as having floating-point precision and storing a fractional value rather than being considered as an integer by default.

What is a string?

In Python, a string is a sequence of characters. It can be made up of letters, numbers, symbols or spaces and it’s enclosed in single quotes (‘ ‘) or double quotes (” “). Strings are one of the most commonly used data types in Python because they represent text values.

For example:

greeting = "Hello, world!"

In this case, greeting is a variable that contains the string "Hello, world!". The quotation marks indicate to Python that this series of characters should be treated as a string.

Strings also have properties (such as length) and methods (such as changing their case or finding substrings). We’ll cover these topics more in-depth in future posts.

Converting a string to a float

In Python, we can show how to convert a string that represents a numerical value (such as “3.14” or “-10”) into its corresponding float number using the built-in function float(). The basic syntax for converting a string to a float is as follows:


where string is the input string we want to convert.

Let’s take an example of converting the string “3.1416” to its corresponding floating-point number:

my_string = "3.1416"
my_float = float(my_string)

This will output:


As you can see, we were able to successfully convert our input string into a floating-point number using the float() function.

Dealing with errors

However, it’s important to note that not all strings are valid inputs for this conversion process. For instance, trying to convert the non-numeric string "hello" would result in an error message:

my_string = "hello"
my_float = float(my_string) # This line raises ValueError!

We get an error message because "hello" cannot be converted into any valid numeric representation and therefore cannot be converted into a float.

To avoid potential errors like this one, it may be helpful use exception handling code when working with user-generated inputs where bad data is more likely – especially if you’re writing code that needs reliable inputs from users who might make mistakes!

When converting strings to floats, errors may occur due to various reasons such as invalid characters in the string or division by zero. It’s important to handle these errors appropriately instead of letting them crash our program.

One common error that might occur is a ValueError which happens when we try to convert a string that does not represent a valid float value. For instance, trying to convert “Hello World!” would raise this error. Another error commonly encountered is ZeroDivisionError which occurs when we attempt to divide by zero.

To handle these errors gracefully, we can use Python’s built-in try-except block. This block allows us to catch any exceptions raised within the try block and execute specific code for each type of exception.

Here’s an example using try-except blocks:

  my_float = float("3.14")
except ValueError:
  print("The passed argument cannot be converted into a float.")
  print("Float conversion successful! The result is:", my_float)

  num = int(input("Enter numerator: "))
  denom = int(input("Enter denominator: "))
  result = num / denom
except ZeroDivisionError:
   print('Cannot divide by zero')

In the above example, if the input entered by the user cannot be casted into an integer (ValueError), then it will jump straight into printing ‘The passed argument…’. If there are no issues with casting data types properly during runtime, then it moves onto else statement where it prints out some message indicating success or computes output values based on those inputs passing through.

Try-except blocks provide us with greater control over how our program handles exceptions making our code more robust and less prone towards crashing due to unexpected scenarios that might arise during execution.

Converting multiple strings to floats

Converting multiple strings to floats is a common operation in data preprocessing for Machine Learning. One way to achieve this is by using loops that iterate through each string and convert them one by one.

Here’s an example of how to convert multiple string values to float using loops in Python:

# Sample list containing string values
string_values = ['3.14', '2.5', '1.618']

# Initialize an empty list for converted float values
float_values = []

# Iterate through each string value and convert it to a float
for s in string_values:
    float_value = float(s)

print(float_values) # [3.14, 2.5, 1.618]

In this code snippet, we first defined a sample list string_values that contains three elements representing decimal numbers as strings (‘3.14’, ‘2.5’, and ‘1.618’). We then initialize an empty list called float_values, which will store the converted floating-point numbers.

Next, we use a loop that iterates over each element of the string_values list and converts it into a floating-point number using the built-in float() function in Python.The resulting float value is appended onto our new empty list called “float values”.

Finally, we print out our new “float values” list containing all the converted numbers as floats.

Overall, using loops can be highly effective when converting multiple strings of data into numerical equivalent forms .


This blog post explores the process of converting a string to a float in Python. The author explains that this is a common task when dealing with numerical data and provides step-by-step instructions for performing the conversion using built-in Python functions. Key points covered also include handling errors that may occur during the conversion process, such as ValueError exceptions.

Additional resources provided in the post include links to relevant documentation on Python’s official website and useful Stack Overflow threads for further reference. By following these guidelines for Python, readers can learn how to convert string to float effectively and avoid potential pitfalls along the way.

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