How to round up/down an int in Python?

Question

Let's say I have an arbitrary integer 874,623,123 how do I round it down to 800,000,000 and up to 900,000,000? Another example is 759 round up to 800 or down to 700. The size of the integer is unknown.

Is there a built-in method to do it? If not, what's the best way to work it out? Sorry not a math expert here.

EDIT: So far I have looked at

Rounding down integers to nearest multiple

Python round up integer to next hundred

Both use a predefined divider

You can use https://stackoverflow.com/a/53975078/4180176 and https://stackoverflow.com/a/13082705/4180176. Honestly a quick google search brings up a bunch of solutions — Joshua Nixon, Jun 10 '21 at 22:08
It answers half of my question, doesn't go to the floor or ceiling. — James Lin, Jun 10 '21 at 22:11
@JoshuaNixon Honestly, if you read my question and read the answers you suggested, it doesn't answer my questions completely, your suggested answers assume a fixed rounding. — James Lin, Jun 10 '21 at 22:16
If you look at the answers, It is very easy to modify the solutions — Joshua Nixon, Jun 10 '21 at 22:17
Can you please [edit] to post which solutions you've already researched and tried. This will avoid people suggesting links and duplicates that does not work for you. — Gino Mempin, Jun 10 '21 at 22:19
Though you're not saying so, it sounds like you want to round to one significant figure. — khelwood, Jun 10 '21 at 22:25
@khelwood they want to ciel/floor to one significant figure I guess — juanpa.arrivillaga, Jun 10 '21 at 22:27
@khelwood thanks, I didn't know how to word it properly, it's not my first language, so I didn't use "significant number" to search for answers. Thanks, that's what I wanted. — James Lin, Jun 10 '21 at 22:28

score 4 · Accepted Answer · edited Jun 10 '21 at 22:43

4

You can use the math module:

import math

n = 874623123

# c contains the same number of digits as n
c = 10 ** int(math.log10(n))

print(math.floor(n/c) * c) # 800000000
print(math.ceil(n/c) * c)  # 900000000

edited Jun 10 '21 at 22:43

ppwater

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answered Jun 10 '21 at 22:17

enzo

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I don' t know why, people having a bad day. I just gave you an upvote. – James Lin Jun 10 '21 at 22:23
I did not downvote. An easier way is to pass a negative `digits` value to `round`. – hilberts_drinking_problem Jun 10 '21 at 22:28
Oh, sorry of the downvote. I thought I upvoted. – ppwater Jun 10 '21 at 22:43

How to round up/down an int in Python?

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