Add some characters at the beginning of each line

Question

I'd like to add some characters to the beginning of each line.

How could I do ?

I was doing that:

'\n\t\t\t'.join(myStr.splitlines())

But it isn't perfect and I'd like to know if there are better ways to do that. I originally want to indent a whole block of text automatically.

Answer 1

For flexible option, you may wish to have a look at textwrap in the standard library.

Example:

>>> hamlet='''\
... To be, or not to be: that is the question:
... Whether 'tis nobler in the mind to suffer
... The slings and arrows of outrageous fortune,
... Or to take arms against a sea of troubles,
... And by opposing end them? To die: to sleep;
... No more; and by a sleep to say we end
... '''
>>> import textwrap
>>> wrapper=textwrap.TextWrapper(initial_indent='\t', subsequent_indent='\t'*2)
>>> print wrapper.fill(hamlet)
    To be, or not to be: that is the question: Whether 'tis nobler in the
        mind to suffer The slings and arrows of outrageous fortune, Or to
        take arms against a sea of troubles, And by opposing end them? To
        die: to sleep; No more; and by a sleep to say we end

You can see that you can not only easily add flexible space on the front of each line, you can trim each line to fit, hyphenate, expand tabs, etc.

It will wrap (hence the name) lines that become too long because of the additions on the front:

>>> wrapper=textwrap.TextWrapper(initial_indent='\t'*3, 
... subsequent_indent='\t'*4, width=40)
>>> print wrapper.fill(hamlet)
            To be, or not to be: that is the
                question: Whether 'tis nobler in the
                mind to suffer The slings and arrows
                of outrageous fortune, Or to take
                arms against a sea of troubles, And
                by opposing end them? To die: to
                sleep; No more; and by a sleep to
                say we end

Very flexible and useful.

Edit

If you wish to keep the meaning of line endings in the text with textwrap, just combine textwrap with splitlines to keep line endings the same.

Example of hanging indent:

import textwrap

hamlet='''\
Hamlet: In the secret parts of Fortune? O, most true! She is a strumpet. What's the news?
Rosencrantz: None, my lord, but that the world's grown honest.
Hamlet: Then is doomsday near.'''

wrapper=textwrap.TextWrapper(initial_indent='\t'*1, 
                             subsequent_indent='\t'*3, 
                             width=30)

for para in hamlet.splitlines():
    print wrapper.fill(para)
    print 

prints

Hamlet: In the secret parts
        of Fortune? O, most true!
        She is a strumpet. What's
        the news?

Rosencrantz: None, my lord,
        but that the world's grown
        honest.

Hamlet: Then is doomsday
        near.

Answer 2

I think that's a pretty nice method. One thing you could improve is that your method introduces a leading newline, and removes any trailing newline. This won't:

'\t\t\t'.join(myStr.splitlines(True))

From the docs:

str.splitlines([keepends])

Return a list of the lines in the string, breaking at line boundaries. This method uses the universal newlines approach to splitting lines. Line breaks are not included in the resulting list unless keepends is given and true.

Also, unless your string begins with a newline, you aren't adding any tabs at the beginning of the string, so you may want to do this too:

'\t\t\t'.join(('\n'+myStr.lstrip()).splitlines(True))