How to replace custom tabs with spaces in a string, depend on the size of the tab?

Question

I\'m trying to write a python function not using any modules that will take a string that has tabs and replace the tabs with spaces appropriate for an inputted tabstop size.

Answer 1

Sorry, i misread the question the first time.

This is a recursive version that should work for any number of tabs in the input :

def tabstop ( s , tabnum = 4):
    if not '\t' in s:
        return s
    l = s.find('\t')
    return s[0:l]+' '*(tabnum-l)+tabstop(s[l+1:],tabnum)

Answer 2

Use the re.sub is enough.

def untabify(s, tabstop = 4):
    return re.sub(re.compile(r'\t'), ' '*tabstop, s)

Answer 3

Fix for @rémi answer This implementation honors the leading tab and any consecutive tabs

def replace_tab(s, tabstop=4):
    result = str()
    for c in s:
        if c == '\t':
            if (len(result) % tabstop == 0):
                result += ' ' * tabstop
            else:
                while (len(result) % tabstop != 0):
                    result += ' '
        else:
            result += c
    return result

Answer 4

Since you wan't a python function that doesn't use any external module, I think you should design first the algorithm of your function...

I would propose to iterate on every char of the string ; if char i is a tab, you need to compute how many spaces to insert : the next "aligned" index is ((i / tabstop) + 1) * tabstop. So you need to insert ((i / tabstop) + 1) * tabstop - (i % tabstop). But an easier way is to insert tabs until you are aligned (i.e. i % tabstop == 0)

def replace_tab(s, tabstop = 4):
  result = str()
  for c in s:
    if c == '\t':
      while (len(result) % tabstop != 0):
        result += ' ';
    else:
      result += c    
  return result

Answer 5

This code can help you:

initial_string = "My \tstring \ttest\t"
block_size = "5"
"".join([("{block_value:"+str(block_size)+"s}").format(block_value=block) 
    for block in initial_string.split("\t")])

You will need to study: format, split and join function and list comprehension concept.

Answer 6

I use .replace function that is very simple:

line = line.replace('\t', ' ')