CODEWITHSUNDEEP
pythonstringpython-3.x
Strahinja
Strahinja

Reputation: 460

Reverse string Python

I would like to get input from a user and then to print the string reversed like this:
input:

hello


output:

o
ol
oll
olle
olleh

This is my code: 

s = input()
for i in range(len(s) - 2, -1, -1):
    print(s[:i:-1])

And output i receive is:

o
ol
oll
olle

I am constantly missing the last character. I tried many variations of the slicing. What am I missing?

Upvotes: 3

Views: 341

Answers (6)

Valdi_Bo
Valdi_Bo

Reputation: 30971

The very basic method to reverse a string s is s[::-1] (and save it in another variable, say s2).

Then, to print consecutive rows with increasing part of this string (s2), you need a loop over range(1, len(s2)+1), stating the upper limit of s2 (excluding).

So the script can look like below:

s = 'hello'
s2 = s[::-1]
for i in range(1, len(s2)+1):
    print(s2[:i])

Upvotes: 0

Patrick Artner
Patrick Artner

Reputation: 51623

You could also simply reverse the complete thing and print it sliced from the start to save you some headache:

b = "hello"   # your input
h = b[::-1]   # inverse all - so this is now olleh

# list slicing is from:exclusive to - so simply add 1 to fit with the ranges values 0-4
for k in ( h[0:i+1] for i in range(0,len(h)) ):
    print(k)

Output:

o
ol
oll
olle
olleh

Upvotes: 0

Anthony Herrera
Anthony Herrera

Reputation: 1

I would do it this way: 

a = "Hello"
for i in range(len(a)):
    print(a[-i-1])

This way you are not dealing with string slices, only indexing the string and there isn't a bunch of extra numbers to figure out what they are doing.

Upvotes: 0

jpp
jpp

Reputation: 164613

Easiest perhaps is to iterate from -1 backwards:

s = 'hello'
for i in range(1, len(s)+1):
    print(s[-1: -i-1: -1])

hello
o
ol
oll
olle
olleh

The way this works, you are slicing sequentially:

  • s[-1: -2: -1],
  • s[-1: -3: -1],...
  • s[-1: -len(s)-1: -1]

Upvotes: 2

user10673977
user10673977

Reputation: 136

To get the full string reversed you must use s[::-1] omitting the first value. Since that doesn't fit into your iteration you'll have to use something like:

s = input()

for i in range(len(s) - 2, -1, -1):
  print(s[:i:-1])

print(s[::-1])

Upvotes: 2

eyllanesc
eyllanesc

Reputation: 243877

You must first obtain the substring and then reverse it:

s = "hello"
for i in range(len(s)-1, -1, -1):
    print(s[i:][::-1])

Or:

s = "hello"
for i, _ in enumerate(s):
    print(s[i:][::-1])

Or reverse the word and get the substring:

s = "hello"
for i, _ in enumerate(s):
    print(s[::-1][:i+1])

Upvotes: 4

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