How to print a string at a fixed width?

I find using str.format much more elegant:

>>> '{0: <5}'.format('s')
's    '
>>> '{0: <5}'.format('ss')
'ss   '
>>> '{0: <5}'.format('sss')
'sss  '
>>> '{0: <5}'.format('ssss')
'ssss '
>>> '{0: <5}'.format('sssss')
'sssss'

In case you want to align the string to the right use > instead of <:

>>> '{0: >5}'.format('ss')
'   ss'

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Edit 1: As mentioned in the comments: the 0 in '{0: <5}' indicates the argument’s index passed to str.format().

---

Edit 2: In python3 one could use also f-strings:

sub_str='s'
for i in range(1,6):
    s = sub_str*i
    print(f'{s:>5}')
    
'    s'
'   ss'
'  sss'
' ssss'
'sssss'

or:

for i in range(1,5):
    s = sub_str*i
    print(f'{s:<5}')
's    '
'ss   '
'sss  '
'ssss '
'sssss'

of note, in some places above, ' ' (single quotation marks) were added to emphasize the width of the printed strings.

format is definitely the most elegant way, but afaik you can't use that with python's logging module, so here's how you can do it using the % formatting:

formatter = logging.Formatter(
    fmt='%(asctime)s | %(name)-20s | %(levelname)-10s | %(message)s',
)

Here, the - indicates left-alignment, and the number before s indicates the fixed width.

Some sample output:

2017-03-14 14:43:42,581 | this-app             | INFO       | running main
2017-03-14 14:43:42,581 | this-app.aux         | DEBUG      | 5 is an int!
2017-03-14 14:43:42,581 | this-app.aux         | INFO       | hello
2017-03-14 14:43:42,581 | this-app             | ERROR      | failed running main

More info at the docs here: https://docs.python.org/2/library/stdtypes.html#string-formatting-operations

Originally posted as an edit to @0x90's answer, but it got rejected for deviating from the post's original intent and recommended to post as a comment or answer, so I'm including the short write-up here.

In addition to the answer from @0x90, the syntax can be made more flexible, by using a variable for the width (as per @user2763554's comment):

width=10
'{0: <{width}}'.format('sss', width=width)

Further, you can make this expression briefer, by only using numbers and relying on the order of the arguments passed to format:

width=10
'{0: <{1}}'.format('sss', width)

Or even leave out all numbers for maximal, potentially non-pythonically implicit, compactness:

width=10
'{: <{}}'.format('sss', width)

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Update 2017-05-26

With the introduction of formatted string literals ("f-strings" for short) in Python 3.6, it is now possible to access previously defined variables with a briefer syntax:

>>> name = "Fred"
>>> f"He said his name is {name}."
'He said his name is Fred.'

This also applies to string formatting

>>> width=10
>>> string = 'sss'
>>> f'{string: <{width}}'
'sss       '

EDIT 2013-12-11 - This answer is very old. It is still valid and correct, but people looking at this should prefer the new format syntax.

You can use string formatting like this:

>>> print '%5s' % 'aa'
   aa
>>> print '%5s' % 'aaa'
  aaa
>>> print '%5s' % 'aaaa'
 aaaa
>>> print '%5s' % 'aaaaa'
aaaaa

Basically:

• the % character informs python it will have to substitute something to a token
• the s character informs python the token will be a string
• the 5 (or whatever number you wish) informs python to pad the string with spaces up to 5 characters.

In your specific case a possible implementation could look like:

>>> dict_ = {'a': 1, 'ab': 1, 'abc': 1}
>>> for item in dict_.items():
...     print 'value %3s - num of occurances = %d' % item # %d is the token of integers
... 
value   a - num of occurances = 1
value  ab - num of occurances = 1
value abc - num of occurances = 1

SIDE NOTE: Just wondered if you are aware of the existence of the itertools module. For example you could obtain a list of all your combinations in one line with:

>>> [''.join(perm) for i in range(1, len(s)) for perm in it.permutations(s, i)]
['a', 'b', 'c', 'd', 'ab', 'ac', 'ad', 'ba', 'bc', 'bd', 'ca', 'cb', 'cd', 'da', 'db', 'dc', 'abc', 'abd', 'acb', 'acd', 'adb', 'adc', 'bac', 'bad', 'bca', 'bcd', 'bda', 'bdc', 'cab', 'cad', 'cba', 'cbd', 'cda', 'cdb', 'dab', 'dac', 'dba', 'dbc', 'dca', 'dcb']

and you could get the number of occurrences by using combinations in conjunction with count().