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Integer division debugging in Python

+1 vote
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The change in integer division seems to be the most insidious source of silent errors in porting code from python2 - since it changes the behavior or valid code silently.

I wish the interpreter had an instrumented mode to detect and report such problems.

posted Aug 28, 2013 by Satish Mishra

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1 Answer

+1 vote
 
Best answer

Run the code under Python 2.6/2.7 with the -3 flag:

$ cat test.py 
print(10 / 7)

$ python -3 test.py
test.py:2: DeprecationWarning: classic int division
 print(10 / 7)
1
answer Aug 28, 2013 by Bob Wise
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+2 votes

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I am using the Linux system with python, i am running the following script

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0 votes

I was following an exercise in a book when I edited the code and came across something I did not get. Here is the relevant part of the code that works:

start=None #initialise 
while start !="": 
 start=input("nStart: ")

 if start:
 start=int(start)
 finish=int(input("Finish: ")) 

 print("word[",start,":",finish,"] is", word[start:finish])

I then changed the code to this:

start=None #initialise 
while start !="": 
 start=int(input("nStart: "))

 if start:

 finish=int(input("Finish: "))

 print("word[",start,":",finish,"] is", word[start:finish])

I combined the int conversion and the input on the same line, rather than to have two different statements. But got an error message:

Traceback (most recent call last):
 File "C:UsersFaisalDocumentspythonpizza_slicer.py", line 23, in 
 start=int(input("nStart: "))
ValueError: invalid literal for int() with base 10: ''

Could someone tell me why I got this error message?

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