Python inserting element into list strange behaviour of infinite loop

Question

I am trying to insert an element into the below list(c5) and obtain new list(c6) when consecutive elements of the list are not same and I have tried below script. This insertion is somehow taking me to infinite loop and I have to kill the program manually to stop the program. Can any one help me to understand this strange behaviour of List in python?

Thanks in advance

c5=['03-03-2017 00:00', '03-03-2017 00:00', '03-03-2017 00:00', '03-03-2017 00:00', '03-03-2017 00:00', '04-03-2017 00:00', '04-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '06-03-2017 00:00', '07-03-2017 00:00', '07-03-2017 00:00', '07-03-2017 00:00', '07-03-2017 00:00', '07-03-2017 00:00', '07-03-2017 00:00', '07-03-2017 00:00', '08-03-2017 00:00', '08-03-2017 00:00', '08-03-2017 00:00', '09-03-2017 00:00', '09-03-2017 00:00', '09-03-2017 00:00', '09-03-2017 00:00', '09-03-2017 00:00', '09-03-2017 00:00', '10-03-2017 00:00']

c6=c5

x=0
for d in c5:
    if(x<(len(c5)-1)):
        if(d != c5[x+1]):
            c6.insert(x+1,'Hurray')
            print(x)
        x+=1

print(c6)

`c6=c5` doesn't make a copy. See https://nedbatchelder.com/text/names.html — user2357112, Mar 15 '17 at 18:29
Possible duplicate of [How to clone or copy a list?](http://stackoverflow.com/questions/2612802/how-to-clone-or-copy-a-list) — TemporalWolf, Mar 15 '17 at 18:43

score 1 · Accepted Answer · answered Mar 15 '17 at 18:29

c5 and c6 reference the same list object due to:

c6=c5

Iteration through c5 in combination with adding to c6 that references the same list means iterating through a list while you're adding elements to it.

Make c6 a copy by using:

c6 = c5[:]

among other options.

Python inserting element into list strange behaviour of infinite loop

1 Answers1