Precision Handling in Python | floor, ceil, round, trunc, format

Learn the different methods for precision handling of floating-point numbers.

Precision handling is a process of rounding off the values of floating-point numbers. Python has many built-in functions to handle the precision, like floor, ceil, round, trunc, and format. Let's discuss the different types of precision handling in Python.

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Some of these methods require the math module to be imported.

floor() function in Python¶

The floor function returns the largest integer less than or equal to a given number. Let's take an example to understand the floor function:

import math

value = 34.185609
print(math.floor(value))
# 34

value = -34.185609
print(math.floor(value))
# -35

ceil() function in Python¶

The ceil function returns the smallest integer greater than or equal to a given number. Let's take an example to understand the ceil function:

import math

value = 34.185609
print(math.ceil(value)
# 35

value = -34.185609
print(math.ceil(value)
# -34

trunc() function in Python¶

The trunc function returns the integer part of a number by removing all the decimal parts from a floating-point number. Let's take an example to understand the trunc function:

import math

value = 34.185609
print(math.trunc(value))
# 34

value = -34.185609
print(math.trunc(value))
# -34

round() function in Python¶

The round function rounds off the output in a customized format. We can pass the number of decimal places as an argument, and it then rounds a number to the given precision in decimal digits. Let's take an example to understand the round function:

value = 34.185609

print(round(value, 2))
# 34.19
print(round(value, 3))
# 34.186
print(round(value, 4))
# 34.1856

Interesting fact: round() can also take a negative integer as second argument:

value = 1346.185609

print(round(value, 0))
# 1346.0
print(round(value, -1))
# 1350.0
print(round(value, -2))
# 1300.0
print(round(value, -3))
# 1000.0

Formatting with f-Strings in Python¶

f-Strings can be used to format values in a String:

value = 34.185609

print(f'The value is: {value:.2f}')
# The value is: 34.19
print(f'The value is: {value:.3f}')
# The value is: 34.186

format() function in Python¶

The format function can also be used to format the output. Let's take an example to understand the format function:

value = 34.185609

print('The value is {0:.2f}'.format(value))
# The value is 34.19

% formatting operator in Python¶

And similar, the % operator can be used to format and set the precision of the output:

value = 34.185609

print('The value is: %.3f' % value)
# The value is: 34.186

Conclusion¶

In this article, we have discussed the different types of precision handling in Python. We have also discussed the different types of formatting in Python.