Python: Replace character in a string based on input

Question

I have a program that takes a string input, and an integer input. The integer determines 2 things, how many times the string is printed, and which character in the string is visible, otherwise replaced by "."

For example - String: Hello World Integer: 3

Should show as:

H..l..W..l.
.e..o..o..d
..l.. ..r..

Basically printing diagonal text.

How would I go about having every 3rd character in the string shown, otherwise replaced by "."? Regardless of the inputted string and beginning with the first.

I only need the function, I got the rest of the code.

The code so far to is this (not compact):

stringVar = input("String: ")
countVar = input("Count: ")

countInt = int(countVar)
stringInt = len(stringVar)

if countInt > stringInt:
    print("Number should be between 1 and the lenght of the string!")
    exit()

if countInt < 1:
    print("Number should be between 1 and the lenght of the string!")
    exit()

count = 1        

while count <= countInt:
    print(stringVar)
    count = count + 1

I just need a way to also replace the characters in StringVar.

Have you made any attempt to write this yourself? If so, can you provide the code? — Ffisegydd
– Ffisegydd, Commented Feb 12, 2014 at 22:22
This reads like homework. Beware, if you take the one line answers below, your teacher will immediately know you didn't do this yourself. — yurisich
– yurisich, Commented Feb 12, 2014 at 22:33

mhlester · Accepted Answer · 2014-02-12 22:30:44Z

2

>>> n = 3
>>> message = 'Hello World'
>>> print ('\n'.join([''.join(['.' if (j-i) % n else c for j, c in enumerate('hello world')]) for i in range(n)]))
h..l..w..l.
.e..o..o..d
..l.. ..r..

The magic happens in (j-i) % n. Modulus is positive if not divisible by n. Beyond that there are two list comprehensions, outer for each line, inner for each character

answered Feb 12, 2014 at 22:30

mhlester

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Comments

Ffisegydd · Accepted Answer · 2014-02-12 22:31:50Z

2

s = 'Hello World!!!'
n = 3
rep = '.'

for j in range(n):
    print(''.join([v if (i - j)%n == 0 else rep for i, v in enumerate(s)]))

# H..l..W..l..!.
# .e..o..o..d..!
# ..l.. ..r..!..

The code iterates over the required number of lines (0,1,2 for n=3). The ''.join(...) method checks if (i - j)%n == 0 to decide when to print the letter, otherwise prints the rep string.

answered Feb 12, 2014 at 22:31

Ffisegydd

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