Append to a string with characters in a while loop python

Question

I'm running into a problem which I cannot solve online- all answers I've found only allow the appending to happen once since it just keeps repeating the same action.

For context: If a string isn't 128 lines long- I want to pad it out to reach 128. All padding should add 00 then move to the next line. For example:

Then with padding should become

01
01
02
03
05
06
09
01
00
00
00
00 UP TO 128 lines

Hope that explains what I need to do.

I've tried using .join and .ljust/.rjust. inside a while loop. The while loop is:

while count != 129:
     padding.join("00\n")
     count += 1

However it only ever prints out 00. Any advice is appreciated. Thank you!

Is using a while loop strictly required here as there's other and more practical methods to do this... — Jon Clements
– Jon Clements, Commented Jul 8, 2022 at 11:07
In your own words, where the code says padding.join("00\n"), exactly what do you expect this to do, and why? What does the name padding mean in your program? What do you expect should be contained in padding after the loop, and how would this help you solve the problem? What is contained in padding after the loop? Please read ericlippert.com/2014/03/05/how-to-debug-small-programs. — Karl Knechtel
– Karl Knechtel, Commented Jul 8, 2022 at 11:13
"Any advice is appreciated. Thank you!" This is not answerable. Please try to come to your best possible understanding of what is going wrong, and then ask a specific question about that. It should start with a question word like "why" or "how", and end with a question mark (?). — Karl Knechtel
– Karl Knechtel, Commented Jul 8, 2022 at 11:15

rasjani · Accepted Answer · 2022-07-08 11:11:53Z

1

your_string = "01\n01\n02\n03\n05\n06\n09\n01\n"
new_string =  your_string + (128 - len(your_string.split())) * "01\n"

answered Jul 8, 2022 at 11:11

rasjani

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Comments

Philip · Accepted Answer · 2022-07-08 11:36:38Z

In order to check the number of lines you need to count the number of "\n" occurrences. Since the string seems to be a variable amount you need to be able to do this dynamically. You would have to write a function to check this.

something like this should work

def pad_string(unpadded_string, string_length =128, pad_string ='00\n'):
    """Function to ensure that a string is ``string_length`` lines.
    Do this by counting the number of new lines and appending deliminator where neccesary"""
    
    num_lines = unpadded_string.count('\n')
    if not num_lines < string_length:
        return unpadded_string
    return unpadded_string + pad_string*(string_length-num_lines)

Using this in your example:

your_string = "01\n01\n02\n03\n05\n06\n09\n01\n"


def pad_string(unpadded_string, string_length =128, pad_string ='00\n'):
    """Function to ensure that a string is ``string_length`` lines.
    Do this by counting the number of new lines and appending deliminator where neccesary"""
    
    num_lines = unpadded_string.count('\n')
    if not num_lines < string_length:
        return unpadded_string
    return unpadded_string + pad_string*(string_length-num_lines)


print(pad_string(your_string).count('\n'))
>>> 128

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