## Rounding

Floats in Python: Techniques and Methods

In the world of programming, precision and accuracy are of utmost importance. Given the complex calculations and mathematical operations that are often required, the presence of even a small error can lead to significant inaccuracies in the final result.

Rounding floats is one of the techniques used to manage this problem.

## Floats in Python

In Python, a float is a floating-point number representing a decimal number. An example of a float in Python is 12.34.

As we know, decimal numbers may have an infinite number of digits in their fractional component. Therefore, when manipulating decimal numbers, it’s important to know how to round these numbers to an appropriate number of decimal places.

Let’s explore a few techniques for rounding floats in Python. 1.

Round a Float to 1, 2 or 3 Decimal Places in Python

Using the “round()” function in Python, we can round a float to a specified number of decimal places. The “round()” function takes the floating-point number and the number of decimal places to round to as arguments.

# Round a single float

num = 12.3456

round_num = round(num, 2)

## print(round_num)

Output: 12.35

In the above example, we’ve rounded the float “num” to two decimal places. The resulting value is “12.35”.

Similarly, we can round a float to one or three decimal places by passing 1 or 3 respectively as the second argument. Multiple floats can also be rounded simultaneously using list comprehension:

# Round a list of floats

lst = [10.23, 23.34, 38.2885, 77.87888]

rounded_lst = [round(num, 2) for num in lst]

## print(rounded_lst)

Output: [10.23, 23.34, 38.29, 77.88]

2. Round a Float to 1, 2 or 3 Decimal Places using f-string

Another way to round a float to a specified number of decimal places is by using formatted string or f-string.

In this approach, we can specify the number of decimal places to round to using the format specification syntax. # Round a single float using f-string

num = 12.3456

rounded_num = f”{num:.2f}”

## print(rounded_num)

Output: 12.35

In the above example, we’ve used the “:.2f” format specification syntax to indicate that we want to round the float “num” to two decimal places. Similarly, we can round to one or three decimal places by using “:.1f” or “:.3f”, respectively.

## A list of floats can also be rounded simultaneously using list comprehension:

# Round a list of floats using f-string

lst = [10.23, 23.34, 38.2885, 77.87888]

rounded_lst = [f”{num:.2f}” for num in lst]

## print(rounded_lst)

Output: [‘10.23’, ‘23.34’, ‘38.29’, ‘77.88’]

3. Round Down Float to 1, 2 or 3 Decimals in Python

Sometimes, we may want to round a float down to a specified number of decimal places.

For this, we can use the “math.floor()” function available in Python. # Round down a single float

## import math

num = 12.3456

floor_num = math.floor(num*100)/100

## print(floor_num)

Output: 12.34

Here, we’ve multiplied the float “num” by 100, rounded it down using the “math.floor()” function and divided it by 100. This creates a “flooring effect”, which rules out the digits beyond the decimal point.

As a result, we get the next lowest decimal point value. A list of floats can also be rounded down simultaneously using list comprehension:

# Round down a list of floats

lst = [10.23, 23.34, 38.2885, 77.87888]

rounded_lst = [math.floor(num*100)/100 for num in lst]

## print(rounded_lst)

Output: [10.23, 23.34, 38.28, 77.87]

4. Round Up Float to 1, 2 or 3 Decimals in Python

Similarly, we may want to round a float up to a specified number of decimal places.

For this, we can use the “math.ceil()” function available in Python. # Round up a single float

## import math

num = 12.3456

ceil_num = math.ceil(num*100)/100

## print(ceil_num)

Output: 12.35

In the above example, we have used the “math.ceil()” function of Python to round the float “num” up to two decimal places. Essentially it works the same way as rounding down, except the ceiling function is used.

## A list of floats can also be rounded up simultaneously using list comprehension:

# Round up a list of floats

lst = [10.23, 23.34, 38.2885, 77.87888]

rounded_lst = [math.ceil(num*100)/100 for num in lst]

## print(rounded_lst)

Output: [10.23, 23.34, 38.29, 77.88]

5. Round a List of Floats to 1, 2, or 3 Decimal Places in Python

To round an entire list of floats to a specific number of decimal places, we can combine our list comprehension techniques with the “round()” function.

# Round a list of floats

lst = [10.23, 23.34, 38.2885, 77.87888]

rounded_lst = [round(num, 2) for num in lst]

## print(rounded_lst)

Output: [10.23, 23.34, 38.29, 77.88]

This code example demonstrates how we can use a single line of code using list comprehension to round all elements within a list down to two decimal places. 6.

Round a List of Floats to 2 Decimal Places using numpy.around()

When dealing with complex computations involving arrays, or if you’re just someone looking for a more efficient way to round, you could use numpy. One of the functions “

## import numpy as np

# Round a list of floats using numpy

lst = [10.23, 23.34, 38.2885, 77.87888]

rounded_lst = np.around(lst, 2)

## print(rounded_lst)

Output: [10.23, 23.34, 38.29, 77.88]

Here, we’ve used the “np.around()” function of numpy to round the given list of floats “lst” to two decimal places.

## Conclusion

In this article, we have covered multiple techniques to round floats in Python. We learned how to round floats to a specific number of decimal places using the “round()” function, f-strings, and numpy.

We also discussed how we can round the float down or up and how these techniques could be used to round a list of floats to a specific number of decimal places. This article is meant for beginners and intermediates looking for quick methods to round floats in Python.

Rounding floats is a common task in many programming languages, including Python. Floats are used to represent decimal values.

However, due to limited memory resources, computers cannot store an infinite number of digits. This means that when manipulating floats, it’s important to ensure that they are rounded to an appropriate number of decimal places.

In this article, we’ll explore some useful techniques and methods for rounding floats in Python. 1.

Round a Float to 1, 2 or 3 Decimal Places in Python

The most straightforward way to round a float to a specified number of decimal places is by using the built-in “round()” function in Python. The “round()” function takes two arguments: the float and the number of decimal places to round to.

For example, to round a float to two decimal places, we can use:

“`

num = 3.1415926

rounded_num = round(num, 2)

## print(rounded_num)

“`

In this example, the “round()” function rounds the float “num” to two decimal places (i.e., 3.14), and the result is assigned to the “rounded_num” variable. We can also require an arbitrary number of decimal places by passing that number as the second argument to the “round()” function.

For example, to round a float to three decimal places, we can use:

“`

num = 3.1415926

rounded_num = round(num, 3)

## print(rounded_num)

“`

In this case, the “round()” function rounds the float “num” to three decimal places (i.e., 3.142), and the result is assigned to the “rounded_num” variable. We can round multiple floats in a list simultaneously using list comprehension.

For example, to round a list of floats to two decimal places, we can use:

“`

lst = [3.1415926, 2.7182818, 1.6180339]

rounded_lst = [round(num, 2) for num in lst]

## print(rounded_lst)

“`

2. Round a Float to 1, 2 or 3 Decimal Places using f-string

Another approach to rounding floats in Python is by using formatted strings (f-strings).

This method allows us to round a float to a specified number of decimal places and convert it to a string in one step. For example, to round a float to two decimal places using f-strings, we can use:

“`

num = 3.1415926

rounded_num = f”{num:.2f}”

## print(rounded_num)

“`

In this example, we’re using an f-string to round the float “num” to two decimal places (i.e., 3.14) and convert it to a string. The “:.2f” in the f-string is the format specifier that indicates that we want to round the float to two decimal places.

Again, we can use f-strings to round multiple floats in a list simultaneously using list comprehension. For example, to round a list of floats to two decimal places using f-strings, we can use:

“`

lst = [3.1415926, 2.7182818, 1.6180339]

rounded_lst = [f”{num:.2f}” for num in lst]

## print(rounded_lst)

“`

3. Round Down Float to 1, 2 or 3 Decimals in Python

Sometimes, we may want to round a float down to a specified number of decimal places.

The “math.floor()” function available in Python can accomplish that. For example, to round a float down to two decimal places, we can use:

“`

## import math

num = 3.1415926

floor_num = math.floor(num * 100) / 100

## print(floor_num)

“`

In this example, we’re multiplying the float “num” by 100, rounding it down using the “math.floor()” function, and dividing it by 100 again to get the decimal point we are interested in. Like the previous methods, we can use list comprehension to round down multiple floats in a list.

For example, to round a list of floats down to two decimal places, we can use:

“`

## import math

lst = [3.1415926, 2.7182818, 1.6180339]

floor_lst = [math.floor(num * 100) / 100 for num in lst]

## print(floor_lst)

“`

4. Round Up Float to 1, 2 or 3 Decimals in Python

Similarly to rounding down, we may want to round a float up to a specified number of decimal places.

For this, we can use the “math.ceil()” function available in Python. For example, to round a float up to two decimal places, we can use:

“`

## import math

num = 3.1415926

ceil_num = math.ceil(num * 100) / 100

## print(ceil_num)

“`

In this example, we’re multiplying the float “num” by 100, rounding it up using the “math.ceil()” function, and dividing it by 100 again to get the decimal point we are interested in. Again, we can use list comprehension to round up multiple floats in a list.

For example, to round a list of floats up to two decimal places, we can use:

“`

## import math

lst = [3.1415926, 2.7182818, 1.6180339]

ceil_lst = [math.ceil(num * 100) / 100 for num in lst]

## print(ceil_lst)

“`

5. Round a List of Floats to 1, 2, or 3 Decimal Places in Python

To round an entire list of floats to a specific number of decimal places, we can combine our list comprehension techniques with the “round()” function.

For example, to round a list of floats to two decimal places, we can use:

“`

lst = [3.1415926, 2.7182818, 1.6180339]

rounded_lst = [round(num, 2) for num in lst]

## print(rounded_lst)

“`

This code example demonstrates how we can use a single line of code using list comprehension to round all elements within a list down to two decimal places. 6.

Round a List of Floats to 2 Decimal Places using numpy.around()

“Numpy”, numerical Python, can be useful when dealing with complex computations involving arrays. One of the functions available in numpy, “np.around()”, allows us to round a list of floats to a specific number of decimal places.

For example, to round a list of floats to two decimal places using numpy, we can use:

“`

## import numpy as np

lst = [3.1415926, 2.7182818, 1.6180339]

rounded_lst = np.around(lst, 2)

## print(rounded_lst)

“`

The “np.around()” function takes in the array of floats “lst” and the desired number of decimal places to round to (i.e., 2 in this example) and returns an array with the rounded values. In conclusion, rounding floats is an essential part of many programming tasks in Python.

This article has covered several methods, including using the “round()” function, f-strings, and numpy. We also explored how to round a float down or up and how to use these techniques to round a list of floats to a specific number of decimal places.

By using these techniques, programmers can ensure that their computations are more accurate and less prone to errors. If you want more information on deep diving into Python coding in general, check out resources like Python Docs and Codecademy.

Rounding floats is an important aspect of many programming tasks in Python. This article covered several methods, including the “round()” function, f-strings, and numpy.

It also explored how to round a float down or up and how to use these techniques to round a list of floats to a specific number of decimal places. By using these techniques, programmers can ensure that their computations are more accurate and less prone to errors.

Rounding floats may seem like a simple task, but it is essential to the accuracy of the final results when dealing with complex computations involving decimal numbers. Remember these methods next time you come across a problem necessitating rounding floats in Python.