Contents

- Why limit decimal places in Python?
- How to limit decimal places in Python using the round() function
- How to limit decimal places in Python using the format() function
- How to limit decimal places in Python using the Decimal module
- How to limit decimal places in Python using the math module
- How to limit decimal places in Python using the fractions module
- How to limit decimal places in Python using the decimal.Context class
- How to limit decimal places in Python using the decimal.localcontext() function
- How to limit decimal places in Python using the round() function with the Decimal module
- How to limit decimal places in Python using the format() function with the Decimal module

Python does not have a built-in round function, but you can use the round() method to round a float to a specified number of decimal places.

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## Why limit decimal places in Python?

When working with floats in Python, it is sometimes useful to limit the number of decimal places that are printed. This can be done with the “round” function. The round function takes two arguments: the number to be rounded and the number of decimal places to keep.

For example, if we have a float with the value 3.14159 and we want to keep only two decimal places, we would use the following code:

“`

>>> x = 3.14159

>>> y = round(x, 2)

>>> print(y)

3.14

“`

## How to limit decimal places in Python using the round() function

Python’s in-built round() function allows us to specify the number of decimal places we want to round off. We can use this round() function along with the print statement to print the required number of decimal places.

In Python, we can use the built-in round() function to easily limit the number of decimal places that are printed. All we need to do is pass in the number we want to round as well as the number of decimal places we want it rounded to.

For example, if we wanted to round the float 1.2345 to 3 decimal places, we would write:

rounded = round(1.2345, 3)

print(rounded)

# 1.235

As you can see from the output, our float was successfully rounded to 3 decimal places.

## How to limit decimal places in Python using the format() function

Python gives you several ways to limit the number of decimal places in a float. You can use the round() function, which rounds a float to a specified number of decimal places. You can also use the format() function, which gives you more control over how a float is displayed as a string.

## How to limit decimal places in Python using the Decimal module

If you want to limit the number of decimal places in a Python float, you can use the Decimal module. This module allows you to specify the number of decimal places you want to round to. For example, if you want to round a float to two decimal places, you can do so like this:

“`

from decimal import Decimal

x = Decimal(‘0.01’)

y = Decimal(‘0.001’)

print(x.quantize(y))

“`

## How to limit decimal places in Python using the math module

The math module in Python contains a number of helpful mathematical functions, including the ceil() function, which can be used to limit decimal places in Python.

To use the ceil() function, simply pass in the number you want to round up, and the number of decimal places you want to round to. For example, to round 3.14159 up to two decimal places, you would use the following code:

import math

rounded = math.ceil(3.14159 * 100) / 100

print(rounded)

This would output 3.15 – as you can see, the original 3.14159 has been rounded up to 3.15.

## How to limit decimal places in Python using the fractions module

The fractions module in Python allows us to represent fractions exactly, and we can use it to limit the decimal places of a float. To do this, we need to first convert the float to a fraction using the Fraction class. We can then use the limit_denominator method to reduce the fraction to its lowest terms and set the maximum denominator. Finally, we can convert the fraction back to a float and print it out.

## How to limit decimal places in Python using the decimal.Context class

If you need to limit the number of decimal places in a Python float, you can use the decimal.Context class. This class allows you to control various aspects of how floating-point numbers are displayed.

To use this class, you first need to create a context object. This object can be created using the decimal.getcontext() function:

import decimal

context = decimal.getcontext()

You can then use the context object to specify the number of decimal places you want to use:

context.prec = 2

With this precision set, all floating-point numbers will now be rounded to two decimal places:

>>> print(decimal.Decimal(1.2345))

1.23

## How to limit decimal places in Python using the decimal.localcontext() function

The decimal.localcontext() function does not round the number, but it limits the number of decimal places that are displayed. It is useful for storing and displaying numbers that are generated by operations with a lot of decimal places, such as when using the math.sqrt() function with large numbers.

To limit the number of decimal places in a Python program, use the decimal.localcontext() function. This function pulls information on the current context from the threading locals structure and creates a new context that is a copy of the current context but with changes made to the prec and rounding attributes. The prec attribute controls how many digits are used when displaying a number, and the rounding attribute controls how numbers are rounded when displayed.

The following example shows how to limit decimal places in Python using the decimal.localcontext() function. The example script first calculates the square root of 100 using the math.sqrt() function:

import math

# calculate the square root of 100

root = math.sqrt(100)

# print root to 20 decimal places without rounding

print(root)

# print root to 20 decimal places with rounding

print(round(root, 20))

The square root of 100 is 10, so when printed to 20 decimal places without rounding, we get 10.000000000000002 as the output (the extra 0s are added because square roots often have an infinite number of decimal places). When rounded to 20 decimal places, we get 10 as expected.

## How to limit decimal places in Python using the round() function with the Decimal module

Python has a built-in round() function that takes two numeric arguments, n and decimals, and returns the number n rounded to decimal places decimals. In this case, the return type is a float. If you want to round to a different type (e.g., int), you can use the second argument, decimals, to specify the number of decimal places you want. For example:

“`

round(1.2345, 2) # Returns 1.23

round(1.2345, 3) # Returns 1.235

“`

If you want to limit a float to 2 decimal places, you can use the string formatting approach “%0.2f” as follows:

“`

“%0.2f” % 1.2345 # Returns “1.23”

“`

Alternatively, if you’re using the Decimal module for exact arithmetic (e.g., financial calculations), you can use the quantize() method with a DecimalContext object to control how many decimal places are used in the result:

“`

from decimal import DecimalContext

c = DecimalContext(prec=2) # prec is short for precision

Decimal(‘1.234’).quantize(c) # Returns Decimal(‘1.23’)

“`

## How to limit decimal places in Python using the format() function with the Decimal module

The Python built-in function round() rounds a floating-point number to the specified number of decimal places. However, sometimes you need more control over the number of decimal places. In this case, you can use the format() function with the Decimal module to control how many decimal places are displayed.

Here’s an example:

“`

>>> from decimal import Decimal

>>> x = Decimal(‘0.123456’)

>>> format(x, ‘.2f’) # 2 decimal places

‘0.12’

“`