*The Python float() method converts a number stored in a string or integer into a floating point number, or a number with a decimal point. Python floats are useful for any function that requires precision*,

*like scientific notation.*

Programming languages use various data types to store values. The type of data a value is stored as will affect how a program can manipulate that value. For instance, you cannot run a string function on an integer or a mathematical operation on a string.

There are two number types in Python: `floating-point numbers (floats)`

and `integers.`

While floats can contain decimals, integers cannot.

This tutorial will discuss the basics of floating-point numbers and how you can use the `float()`

method to convert strings and integers to floats in Python. We’ll also walk through programming examples that employ the `float()`

method to convert integers and strings to floating-point numbers.

## Python Float

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Any numerical value entered into Python will be seen as a number, so it’s not necessary to declare that a value is a number. When you insert a value without decimals, Python will interpret it as an integer (e.g., 24 or -72); values that include decimals will be interpreted as floats (e.g., 102.2 or -4.91).

Integers include positive whole numbers (e.g., 3, 7, 26), their negative counterparts (e.g., -3, -7, -26), and 0. In Python, integers are commonly referred to using the term `int`

. Here’s an example of a program that prints out an integer to the console:

print(4)

Our code returns: `4`

.

Floating-point numbers, on the other hand, are real numbers. Unlike integers, floating-point numbers can store decimal values.

Here’s a program that prints out a floating-point number to the console:

print(3.14)

Our code returns: `3.14`

.

Because both integers and floats are numbers (in terms of their data type), we can perform mathematical operations on them. So, if we wanted to perform floating-point arithmetic and add two floats together, for example, we could do so using the following code:

math_sum = 22.5 + 17.4 print(math_sum)

Our code computes 22.5 + 17.4, and then returns: `39.9`

.

## Python float() Method

The `float()`

method is a built-in Python function that is used to convert an integer or a string to a floating-point value.

Here’s the syntax for the `float()`

method in Python:

float(value)

The `float()`

method takes in one parameter: the value you want to convert to a float. This parameter is optional and its default value is 0.0.

## Converting an Integer to a Float in Python

You can use the `float()`

method in Python to convert an integer to a floating-point number. Here’s an example:

float_number = float(12) print(float_number)

Our code returns: `12.0`

.

Here, we used the `float()`

method to convert an integer `(12)`

into a floating-point number `(12.0)`

. The `.`

at the end tells us that our number has successfully been converted to a floating-point value.

## Converting a String to a Float in Python

In Python, a string is a sequence of characters. Just as `float()`

can convert an integer to a floating-point number, it can convert a string to a floating-point number as well. To do so, the string must be numerical.

Here’s an example of `float()`

being used to convert a string to a floating-point number in Python:

float_string = float("12") print(float_string)

Our code returns: `12.0`

.

In this example, a numerical value `(12)`

was stored as a string in our program. The `float()`

method converted this value into a floating-point number.

You can use the `+`

and `-`

signs to denote whether you want your string to be converted to a positive float or a negative float. Here’s an example of this in action:

float_string = float("-12") print(float_string)

Our code returns: `-12.0`

. Notice that our data is now stored as a float, rather than a string. This is evident because our number is not in quotation marks, and ends with `.`

.

Strings can also contain `NaN`

, `infinity`

, or `inf`

. These combinations of letters are used to represent invalid numbers (`NaN`

) and infinity values (`infinity`

or `inf`

).

## Python Float(): Example

Let’s walk through a more detailed example to show how to use the `float()`

method in Python.

Say that we are creating a math game for fourth-grade students who are learning about adding and subtracting decimal numbers. This game will give students a math problem to solve and will evaluate whether their responses are accurate. Because we are working with decimals, we’ll want our code to convert each number to a float.

Here’s the code we could use to create this game:

answer = round(12.2 + 14.6, 1) student_input = input("What is 12.2 + 14.6?") if float(student_input) == answer: print("You're right!") else: print("The correct answer to 12.2 + 14.6 is", answer, ".")

When we run our code and input the correct answer `(26.8)`

in response to the prompt, our code returns the following:

What is 12.2 + 14.6? 26.8 You're right!

When we run our code and input the incorrect answer (for example, -2.4) in response to the prompt, our code returns the following:

What is 12.2 + 14.6? -2.4 The correct answer to 12.2 + 14.6 is 26.8.

Let’s break down our code. On the first line, we calculate the answer to a math problem (12.2 + 14.6) and use the `round()`

method to make sure we have a value that is rounded to one decimal place.

Then, we use the `input()`

method to ask a student to input an answer to the math problem. The parameter of the input method here is the question our program will ask students (`What is 12.2 + 14.6?`

)

On the next line, we use an `if`

statement to compare whether the student’s answer is equal to the answer our program calculated. Importantly, we use the `float()`

method to convert the variable `student_input`

to a float. We must do this because the `input()`

method returns data in a string format, and we cannot compare a string to a float. So, in order for our program to work, we needed to convert `student_input`

to a float.

If a student enters the correct answer, the message `You’re right!`

is printed to the console; otherwise, the console prints the correct answer, which follows the text we set to precede the answer (`The correct answer to 12.2 + 14.6 is`

).

## Conclusion

Floating-point numbers are a crucial part of programming. They allow developers to work with decimal values. This tutorial discussed the basics of floating-point values in Python and walked through a few examples of how to use the `float()`

method to convert integers and strings to floating-point numbers.

You’re now ready to start working with floating-point numbers and the built-in Python `float()`

method like an expert!

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