New submission from Pradnyan <paraak...@gmail.com>:
I have come across very strange Python bug in nested for loops:
See below nested for loop with range function and its not working as expected.
It worked fine until cnt=2136 and start giving unexpected output after that.
As per logic y value should get incremented for every x value but after
cnt=2136 the y value remains 0 and x gets incremented and also
code did not stop for cnt>2137 and it halts only at 5352.
I have attached actual python code and its output. This code is executed on
latest python build 3.7.3
Erroneous output
================================================================
cnt=2134 y=2133 x=0
cnt=2135 y=2134 x=0
cnt=2136 y=2135 x=0
cnt=2137 y=0 x=1
cnt=2138 y=1 x=1
cnt=2139 y=0 x=2
cnt=2140 y=0 x=3
cnt=2141 y=0 x=4
==================================================================
==================================================================
Python code:
==================================================================
cnt=0
for x in range(3216):
for y in range(2136):
cnt = cnt + 1
#print("y="+str(y)+" x="+str(x)+" pixel="+str(im_ary[y,x]))
print("cnt="+str(cnt)+" y=" + str(y) + " x=" + str(x) )
if cnt>2137 :
break
=================================================================
----------
components: Build
files: Pyton_For_Loop_issue.zip
messages: 346884
nosy: anthonybaxter, barry, benjamin.peterson, eric.araujo, ezio.melotti,
georg.brandl, gvanrossum, lemburg, mdk, ned.deily, pradnyan, tarek
priority: normal
severity: normal
status: open
title: Nested For Loop in Python not working as Expected after cnt=2136
type: behavior
versions: Python 3.7
Added file: https://bugs.python.org/file48444/Pyton_For_Loop_issue.zip
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue37447>
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