CODEWITHSUNDEEP
pythonlistrounding
mrzippy01
mrzippy01

Reputation: 383

Rounding a list of floats into integers in Python

I have a list of numbers which I need to round into integers before I continue using the list. Example source list:

[25.0, 193.0, 281.75, 87.5, 80.5, 449.75, 306.25, 281.75, 87.5, 675.5,986.125, 306.25, 281.75]

What would I do to save this list with all of the numbers rounded to an integer?

Upvotes: 16

Views: 51479

Answers (8)

snark
snark

Reputation: 2897

If your original list of floats is in a numpy array you can use numpy.rint(). Somewhat annoyingly, although it rounds floating point values to the nearest integer, it still leaves them as floats, so you also have to cast them to ints afterwards. Example:

import numpy as np
x = np.array([2.0, -1.6, -1.2,  0.5, 1.5, 2.5, 2.45, 2.55, 1.8])
rounded = np.rint(x).astype(int)

# If you want to convert the array back into a regular Python list:
print(rounded.tolist())  # [2, -2, -1, 0, 2, 2, 2, 3, 2]

Upvotes: 0

brodegon
brodegon

Reputation: 251

If you would set the number of significant digits you could do

new_list = list(map(lambda x: round(x,precision),old_list))

Furthermore, if you had a list of list you could do

new_list = [list(map(lambda x: round(x,precision),old_l)) for old_l in old_list]

Upvotes: 4

zondo
zondo

Reputation: 20336

You could use the built-in function round() with a list comprehension:

newlist = [round(x) for x in list]

You could also use the built-in function map():

newlist = list(map(round, list))

I wouldn't recommend list as a name, though, because you are shadowing the built-in type.

Upvotes: 13

C.Nivs
C.Nivs

Reputation: 13106

Updating this for python3 since other answers leverage python2's map, which returns a list, where python3's map returns an iterator. You can have the list function consume your map object:

l = [25.0, 193.0, 281.75, 87.5, 80.5, 449.75, 306.25, 281.75, 87.5, 675.5,986.125, 306.25, 281.75]

list(map(round, l))
[25, 193, 282, 88, 80, 450, 306, 282, 88, 676, 986, 306, 282]

To use round in this way for a specific n, you'll want to use functools.partial:

from functools import partial

n = 3
n_round = partial(round, ndigits=3)

n_round(123.4678)
123.468

new_list = list(map(n_round, list_of_floats))

Upvotes: 1

Artem Yevtushenko
Artem Yevtushenko

Reputation: 702

NumPy is great for handling arrays like this.
Simply np.around(list) or np.round(list) works.

Upvotes: 2

Mauro Baraldi
Mauro Baraldi

Reputation: 6575

Another approach using map function.

You can set how many digits to round.

>>> floats = [25.0, 193.0, 281.75, 87.5, 80.5, 449.75, 306.25, 281.75, 87.5, 675.5,986.125, 306.25, 281.75]
>>> rounded = map(round, floats)
>>> print rounded
[25.0, 193.0, 282.0, 88.0, 80.0, 450.0, 306.0, 282.0, 88.0, 676.0, 986.0, 306.0, 282.0]

Upvotes: 2

ᴀʀᴍᴀɴ
ᴀʀᴍᴀɴ

Reputation: 4528

Simply use round function for all list members with list comprehension :

myList = [round(x) for x in myList]

myList # [25, 193, 282, 88, 80, 450, 306, 282, 88, 676, 986, 306, 282]

If you want round with certain presicion n use round(x,n):

Upvotes: 24

Mark Skelton
Mark Skelton

Reputation: 3891

You can use python's built in round function.

l = [25.0, 193.0, 281.75, 87.5, 80.5, 449.75, 306.25, 281.75, 87.5, 675.5,986.125, 306.25, 281.75]

list = [round(x) for x in l]

print(list)

The output is:

[25, 193, 282, 88, 80, 450, 306, 282, 88, 676, 986, 306, 282]

Upvotes: 2

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