When working with floating-point numbers in Python, it’s often necessary to limit the number of decimal places to a specific number. In many cases, two decimal points are sufficient, particularly when working with currency, percentages, or any other application that requires accurate rounding. In this blog post, we will explore different ways to limit floats to two decimal points in Python.
Method 1: Using the round() function
One of the easiest ways to limit floats to two decimal points is by using the built-in round() function. The round() function takes two arguments: the number to be rounded and the number of decimal places to round to.
Here’s an example of how to use the round() function to limit a float to two decimal points:
# Example 1 - using the round() function
num = 3.141592653589793
rounded_num = round(num, 2)
print(rounded_num)
Output:
3.14
In the above example, we passed the number num (which has many decimal places) to the round() function along with the number of decimal places we want to round to (2 in this case). The output of the round() function is the float 3.14.
Method 2: Using string formatting
Another way to limit floats to two decimal points in Python is by using string formatting. In Python, string formatting is a way of creating formatted strings by substituting values into placeholders in a string. We can use string formatting to round a float to two decimal places.
Here’s an example of how to use string formatting to limit a float to two decimal points:
# Example 2 - using string formatting
num = 3.141592653589793
formatted_num = "{:.2f}".format(num)
print(formatted_num)
Output:
3.14
In the above example, we used the "{:.2f}" format specifier to format the float num to two decimal places. The ".2f" specifies that the number should be formatted to two decimal places. The output of the string formatting operation is the float 3.14.
Method 3: Using the decimal module
The decimal module in Python provides support for decimal floating-point arithmetic. It offers more precision than the built-in float type and is particularly useful for financial and monetary calculations where precision is critical. We can use the decimal module to limit a float to two decimal points.
Here’s an example of how to use the decimal module to limit a float to two decimal points:
# Example 3 - using the decimal module
from decimal import Decimal
num = 3.141592653589793
decimal_num = Decimal(num).quantize(Decimal('.01'))
print(decimal_num)
Output:
3.14
In the above example, we first imported the Decimal class from the decimal module. We then passed the float num to the Decimal constructor to convert it to a Decimal object. We then used the quantize() method to round the Decimal object to two decimal places. The output of the quantize() method is a Decimal object with the value 3.14.
Method 4: Using the numpy module
The numpy module is a popular Python library for scientific computing. It provides support for arrays and matrices and a wide range
of mathematical operations, including rounding. We can use the numpy module to limit a float to two decimal points.
Here’s an example of how to use the numpy module to limit a float to two decimal points:
# Example 4 - using the numpy module
import numpy as np
num = 3.141592653589793
numpy_num = np.round(num, 2)
print(numpy_num)
Output:
3.14
In the above example, we first imported the numpy module using the alias np. We then used the np.round() function to round the float num to two decimal places. The output of the np.round() function is the float 3.14.
Method 5: Using the math module
The math module is another built-in Python module that provides mathematical functions. The math module has a floor() function that rounds a number down to the nearest integer. We can use this function along with some simple arithmetic to round a float to two decimal points.
Here’s an example of how to use the math module to limit a float to two decimal points:
# Example 5 - using the math module
import math
num = 3.141592653589793
rounded_num = math.floor(num * 100) / 100
print(rounded_num)
Output:
3.14
In the above example, we first imported the math module. We then multiplied the float num by 100 to shift the decimal point two places to the right. We then used the math.floor() function to round the result down to the nearest integer. Finally, we divided the rounded number by 100 to shift the decimal point back to its original position. The output of this operation is the float 3.14.
Conclusion
In this blog post, we explored five different methods for limiting floats to two decimal points in Python. We looked at using the round() function, string formatting, the decimal module, the numpy module, and the math module. While each of these methods has its own advantages and disadvantages, they all provide a way to round floats to a specific number of decimal places.
Whether you’re working with currency, percentages, or any other application that requires accurate rounding, it’s important to know how to limit floats to two decimal points. With the methods described in this blog post, you should now be able to do just that.