[ Python 常見問題 ] How to format print output or string into fixed width?

Source From Here 
Question 
I have this code (printing the occurrence of the all permutations in a string): 

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1. def splitter(str):  
2.     for i in range(1, len(str)):  
3.         start = str[0:i]  
4.         end = str[i:]  
5.         yield (start, end)  
6.         for split in splitter(end):  
7.             result = [start]  
8.             result.extend(split)  
9.             yield result      
10.   
11. el =[];  
12.   
13. string = "abcd"  
14. for b in splitter("abcd"):  
15.     el.extend(b);  
16.   
17. unique =  sorted(set(el));  
18.   
19. for prefix in unique:  
20.     if prefix != "":  
21.         print "value  " , prefix  , "- num of occurrences =   " , string.count(str(prefix));  

I want to print all the permutation occurrence there is in string varaible. since the permutation aren't in the same length i want to fix the width and print it in a nice not like this one: 

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1. value   a - num of occurrences =    1  
2. value   ab - num of occurrences =    1  
3. value   abc - num of occurrences =    1  
4. value   b - num of occurrences =    1  
5. value   bc - num of occurrences =    1  
6. value   bcd - num of occurrences =    1  
7. value   c - num of occurrences =    1  
8. value   cd - num of occurrences =    1  
9. value   d - num of occurrences =    1  

How can I use format to do it? 

How-To 
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: 

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1. >>> print("|%5s" % 'aa')  
2. |   aa  
3. >>> print("%5s" % 'aaa')  
4. |  aaa  
5. >>> print("%5s" % 'aaaa')  
6. | aaaa  
7. >>> print("%5s" % 'aaaaa')  
8. |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.

If you are using format function from string class: 

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1. >>> print("{:^>5s}".format('a'))  # '^ 'as filler; '>' as align policy; '5' as width  
2. ^^^^a  
3. >>> print("{:^>5s}".format('aa'))  
4. ^^^aa  
5. >>> print("{:^>5s}".format('aaa'))  
6. ^^aaa  
7. >>> print("{:^>5s}".format('aaaa'))  
8. ^aaaa  
9. >>> print("{:^>5s}".format('aaaaa'))  
10. aaaaa  

In your specific case a possible implementation could look like: 

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1. >>> dict_ = {'a': 1, 'ab': 1, 'abc': 1}  
2. >>> for item in dict_.items():  
3. ...     print 'value %3s - num of occurances = %d' % item # %d is the token of integers  
4. ...   
5. value   a - num of occurances = 1  
6. value  ab - num of occurances = 1  
7. 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: 

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1. >>> import itertools as it  
2. >>> it.permutations(['a', 'b'], 1)  
3.  0x7f8994e3e470>  

>>> list(it.permutations(['a', 'b'], 1))  

[('a',), ('b',)]  

>>> list(it.permutations(['a', 'b'], 2))  

[('a', 'b'), ('b', 'a')]  

>>> [''.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', ...]