Jupyter Notebook, Python3 print function: No output, No error

Question

Refer to the CODE and OUTPUT below. There is no OUTPUT for the third print statement. An altered print statement in its place such as print(long_word[3:7]) gives output (elin).

# [ ] print the first 4 letters of long_word
# [ ] print the first 4 letters of long_word in reverse
# [ ] print the last 4 letters of long_word in reverse
# [ ] print the letters spanning indexes 3 to 6 of long_word in Reverse
long_word = "timeline"
print(long_word[:4])
print(long_word[3::-1])
print(long_word[3:7:-1])
print(long_word[-1:-5:-1])

OUTPUT

time
emit

enil

What gives? The situation of this question also raised in link below. It is unaddressed as of now.

danche · Accepted Answer · 2017-06-18 03:04:27Z

1

The slice operation in Python is [start:end:step], when step=-1, it represents get values in the reverse direction.

So when use print(long_word[3::-1]), it is actually from index 3 to index 0 which is determined by reverse direction flag step=-1. But when use print(long_word[3:7:-1]), it represents from index 3 to index 7 which is not a reverse order and it is a collision.

answered Jun 18, 2017 at 3:04

danche

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2 Comments

Pankaj113 Over a year ago

Right, so it should be print(long_word[6:2:-1]) This works. One would expect an error in the above case of collision, no?

danche Over a year ago

I think it is not an error, as you can use print(long_word[2:15]) or print(long_word[3:1]). It is just not a rational range.

TrampolineTales · Accepted Answer · 2017-09-11 15:31:16Z

0

If you want to print last four letters in reverse try the below code:

long_word = "Characteristics" 

print(long_word[14:10:-1])

Result: scit

14 is a starting string index
10 is an ending string index
-1 is used to reverse the string one by one

edited Sep 11, 2017 at 15:31

TrampolineTales

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answered Sep 11, 2017 at 14:40

kirankumar M

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Comments

salman · Accepted Answer · 2018-05-20 11:50:53Z

0

long_word = "timeline"

print(long_word[0:4])

print(long_word[3::-1])

print(long_word[-1:3:-1])

print(long_word[-3:-7:-1])

This is what I have tried, I think it is an answer of your question.

answered May 20, 2018 at 11:50

salman

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Comments

Mohsen Kadoura · Accepted Answer · 2018-07-07 09:51:22Z

0

The correct code is:

    long_word = "timeline"
    print(long_word[:4])
    print(long_word[3::-1]) 
    print(long_word[-1:-5:-1])
    print(long_word[6:2:-1])

time
emit
enil
nile

Note that when reversing, you state the wanted ending index first, then the wanted start index - 1 second(except for the 0 index do not subtract one from it), like so:

long_word(wanted ending index: wanted start index - 1: -1)

edited Jul 7, 2018 at 9:51

answered Jul 6, 2018 at 14:50

Mohsen Kadoura

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1 Comment

Nico Haase Over a year ago

Can you highlight the neccessary changes?

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