How to print (all) the result(s) of a while loop in reverse order?

Question

#decimalToBinary

num=int(input("Enter number"))

while num!=0:
    bin=num%2
    num=num//2
    print(bin,end=" ")

Let's say the input,here, is 13. It'll give the output:1 0 1 1.
How can I print it in reverse (i.e, 1 1 0 1) ?

Divyanshu Srivastava · Answer 1 · 2019-05-24T09:30:22.133

3

Store it in a list, then print it in reverse.


#decimalToBinary

num=int(input("Enter number"))
output = []
while num!=0:
    bin=num%2
    num=num//2
    output.append(bin)

print (output[::-1])

To print the results as a string

print (' '.join([str(o) for o in output[::-1]]))

EDIT As suggested in comments, Here is the approach avoiding lists.

#decimalToBinary

num=int(input("Enter number"))
output = ''
while num!=0:
    bin=num%2
    num=num//2
    output = str(bin) + output

print (output)

edited May 24 '19 at 09:30

answered May 21 '19 at 14:28

Divyanshu Srivastava

1,379
11
24

Thanks, it works. The output now is: [1, 1, 0, 1] . Any suggestions for how to remove the comma(s)? – The_L0s3r. May 21 '19 at 14:37
use `print (''.join([str(o) for o in output[::-1]]))` – Divyanshu Srivastava May 21 '19 at 14:38
@DivynshSrivstv . Thanks, it works. There's a shorter version of it though: – The_L0s3r. May 23 '19 at 13:53
@DivynshSrivstv .Replacing `output=[]` with `output=''` ; `output.append(bin)` with `output=str(bin)+output` and the final statement(s) with `print(output)`. – The_L0s3r. May 23 '19 at 14:02
@The_L0s3r. Updated my answer. Please have a look. – Divyanshu Srivastava May 24 '19 at 09:31

score 1 · Answer 2 · answered May 21 '19 at 14:31

Without resorting to some more difficult tricks trying to manipulate where you print things in a console, it might be easier to build up a string in the loop:

num=int(input("Enter number"))
digits = []
while num!=0:
    bin=num%2
    num=num//2
    digits.append(bin)

and reverse it afterwards:

print(digits[::-1]) #this will possibly need formatting.

To format this with spaces try:

print(" ".join(str(x) for x in L[::-1]))

score 1 · Accepted Answer · answered May 21 '19 at 14:32

1

You can build the whole result in a string, then reverse it :

num = 13
bin = ""
while num!=0:
    bin += str(num%2) + " "
    num=num//2

bin = bin.strip();

print(bin[::-1])

Outputs :

1 1 0 1

answered May 21 '19 at 14:32

Cid

14,968
4
30
45

score 0 · Answer 4 · answered May 21 '19 at 14:30

0

for your example this should work:

num=int(input("Enter number"))
lst=list()
while num!=0:
    bin=num%2
    num=num//2
    lst.append(bin)

print(lst,lst[::-1])

output:

Enter number13
[1, 0, 1, 1] [1, 1, 0, 1]

answered May 21 '19 at 14:30

Mig B

637
1
11
19

This is an exact replica of my answer. – Divyanshu Srivastava May 21 '19 at 14:37

score 0 · Answer 5 · answered May 21 '19 at 14:57

Well, you could append the values of bin in an array or just make bin an array and append to it and then print the array in reverse.

from __future__ import print_function
num=int(input("Enter number"))
bin = []
while num!=0: 
    bin.append(num%2) 
    num=num//2
print(*bin[::-1], sep=' ')

How to print (all) the result(s) of a while loop in reverse order?

5 Answers5