Python Limit Floats to Two Decimal Points

How to limit floats to two decimal points in Python? One solution to limit floats to two decimal points is to use the round() function, which rounds a number to a specified number of decimal points.

1. Quick Examples of Limiting Floats to Two Decimal Points

These are examples of different methods of limiting floats to two decimal points in Python. These examples should give you a high-level overview of each method and its syntax.


# Quick examples of limiting floats to two decimal points 

# Example 1: Using the round() function
rounded_num = round(num, 2)
print(rounded_num)

# Example 2: Using string formatting
rounded_num = "{:.2f}".format(num)
print(rounded_num)

# Example 3: Using f-strings
rounded_num = f"{num:.2f}"
print(rounded_num)

# Example 4: Using the format() function
rounded_num = format(num, ".2f")
print(rounded_num)

2. round() – Round up Floats to Two Decimal Points

To limit a float to two decimal points use the Python round() function, you simply need to pass the float as the first argument and the value 2 as the second argument.

The round() function is used to round a number to a specified number of decimal points. By default, round() rounds to the nearest integer, but you can specify the number of decimal points by passing a second argument to the function.

See the following Example:


# Using round()
num = 3.141592653589793
rounded_num = round(num, 2)
print("Float rounded up to two decimal points:", rounded_num)

Yields below output.

The round() function uses the “Round Half to Even” rule, also known as “banker’s rounding”. If you round 2.5 to one decimal point using round(2.5, 1), the result will be 2.4, not 2.5.

This is because 2.5 is exactly halfway between 2.4 and 2.6, so round() rounds down to the nearest even number (2), rather than up to the nearest odd number (3).

Look at the following example to understand the “Round Half to Even”:


# round() examples
num1 = 2.5
num2 = 3.5
rounded_num1 = round(num1, 0)
rounded_num2 = round(num2, 0)

print(rounded_num1) 
# output: 2.0

print(rounded_num2) 
# output: 4.0

num1 is exactly halfway between 2 and 3, so round() rounds down to the nearest even number (2).
Similarly, num2 is exactly halfway between 3 and 4, so round() rounds up to the nearest even number (4).

3. String Formatting to Limit Float to Specific Points

Formatted String is an important feature of Python. We can use it to control the way numbers are displayed by specifying formatting options.

To limit a float to two decimal points using Python string formatting, you can use the format string {:.2f}, where the 2 specifies the number of decimal points to display and the f indicates that the argument should be formatted as a float.


# Using string formatting
formatted_num = "{:.2f}".format(num)
print(formatted_num)

With String formatting, we can easily concatenate the number with a larger string. See the following example:


# String formatting examples
dollars = 1234567.89
formatted_dollars = "${:,.2f}".format(dollars)
print(formatted_dollars)

# Output: 
# $1,234,567.89

String formatting can also be achieved using the f-string syntax. To limit a float to two decimal points using f-strings, you can include the expression inside braces ({}) and use the format string :.2f.


# Using f-string
formatted_num = f"{num:.2f}"
print(formatted_num)

# Output: 3.14

4. Use Decimal Module

Python’s built-in decimal module provides support for exact decimal arithmetic, which can be useful when working with financial or other numerical data that requires precise calculations.

To limit a float to two decimal points using the decimal module, you can create a Decimal object from the float and then use the quantize() method to round the value to the desired number of decimal places.


# Import decimal module
from decimal import Decimal

num = 3.141592653589793
decimal_num = Decimal(str(num))
rounded_num = decimal_num.quantize(Decimal('.01'))
print(rounded_num)

# Output: 3.14

You can specify different rounding modes (e.g., rounding up or down) or adjust the precision of the calculation to more than two decimal points if necessary.


from decimal import Decimal, ROUND_HALF_UP

dollars = 1234567.895
decimal_dollars = Decimal(str(dollars))
rounded_dollars = decimal_dollars.quantize(Decimal('.01'), rounding=ROUND_HALF_UP)
formatted_dollars = "${:,.2f}".format(rounded_dollars)
print(formatted_dollars)

# Output: $1,234,567.90

Frequently Asked Questions on Python Limit Floats to Two Decimal Points

How can I round a float to two decimal points in Python?

You can use the round() function or format the float as a string using the format() method or f-strings.

Can I achieve precise decimal rounding using the decimal module?

You can achieve precise decimal rounding using the decimal module in Python. The decimal module provides the Decimal data type, which allows for more control over precision and rounding compared to the built-in float type.

What’s the difference between rounding and formatting for two decimal points?

Rounding with round() alters the numerical value, while formatting as a string preserves the original value but displays it with the specified precision. Choose based on your specific use case.

Are there performance considerations when using the decimal module?

The decimal module can be slower than working with native floats due to increased precision and complexity. Use it when precise decimal arithmetic is necessary, such as in financial applications.

How do I choose between rounding methods?

The choice of rounding method (rounding down, up, or to the nearest) depends on your specific requirements. Use round() or math.ceil() for rounding, and the decimal module for precise control over rounding methods.

Summary and Conclusion

We have explained multiple ways to limit floats to two decimal points in Python. You have learned the round() function, string formatting, f-strings, the Decimal module. I hope this article was helpful. Leave your queries in the comment section.

Happy Coding!!