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Created on 2017-04-07 04:02 by nvutri, last changed 2022-04-11 14:58 by admin. This issue is now closed.
| Files | ||||
|---|---|---|---|---|
| File name | Uploaded | Description | Edit | |
| int_bug.py | nvutri, 2017-04-07 04:02 | Code to reproduce error for int | ||
| Messages (3) | |||
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| msg291249 - (view) | Author: Tri Nguyen (nvutri) | Date: 2017-04-07 04:02 | |
This code below shows a situation when Python int() library would return a value of int(1.0) -> 0.0
---------------CODE----------------------------
CHANGES = [1.00, 0.50, 0.25, 0.10, 0.05, 0.01]
# This code was originally to solve the least number of changes needed.
# However, in an attempt to solve this. A bug is found.
def get_change(R):
for change in CHANGES:
# This division and int() is where failure is happening
num = int(R / change)
# This printing line shows the failure.
print 'int(%s)\t = %s' % (R / change, num)
R = R - num * change
print 'R = %s' % R
get_change(4.01)
-------------OUTPUT----------------------
int(4.01) = 4
int(0.02) = 0
int(0.04) = 0
int(0.1) = 0
int(0.2) = 0
int(1.0) = 0 # This should be 1, right?
R = 0.01
|
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| msg291250 - (view) | Author: Eryk Sun (eryksun) *  |
Date: 2017-04-07 04:19 | |
Use %r instead of %s to show the repr. Hopefully that should clear things up for you. int() truncates toward 0. The float in this case is slightly less than 1. |
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| msg291251 - (view) | Author: Serhiy Storchaka (serhiy.storchaka) *  |
Date: 2017-04-07 04:20 | |
"%s" rounds float representation to 12 digits in Python 2.7. Replace "%s" with "%r" and you will get precise representation of floats. int(4.01) = 4 int(0.019999999999999574) = 0 int(0.03999999999999915) = 0 int(0.09999999999999787) = 0 int(0.19999999999999574) = 0 int(0.9999999999999787) = 0 R = 0.009999999999999787 See also https://docs.python.org/2/tutorial/floatingpoint.html . |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:58:45 | admin | set | github: 74195 |
| 2017-04-07 04:20:16 | serhiy.storchaka | set | nosy:
+ serhiy.storchaka messages: + msg291251 |
| 2017-04-07 04:19:16 | eryksun | set | status: open -> closed nosy: + eryksun messages: + msg291250 resolution: not a bug stage: resolved |
| 2017-04-07 04:02:05 | nvutri | create | |