Reversing a string

[Duncan Booth]

Martin Durkin <nospam at williamsdurkin.co.uk> wrote:

>>>>> def rev(x):
>>             mylist = []
>>             for char in x:
>>                  mylist.append(char)
>>             mylist.reverse()
>>             for letter in mylist:
>>                  print letter
>> 
>> However, compare the incredible difference in clarity and elegance
>> between that and:
>> 
>>> >>> print "\n".join("spam"[::-1])
>> 
> 
> OK, maybe I'm missing the point here as I'm new to Python. The first one 
> seems clearer to me. What am I missing?
> 
I think all you are missing is familarity with Python, but I too don't like 
one-liners simply for their own sake.

Slicing is one of Pythons great features, but even experienced programmers 
often forget that you can have a third argument to a slice or that it can 
even be negative.

The syntax for joining a sequence of strings with a separator is ugly, I 
sometimes prefer to write it out as:
   print str.join('\n', whatever)
or:
   joinlines = '\n'.join
   ...
   print joinlines(whatever)

but in this case I'd be as likely to go for an explicit loop for the print:

def rev(x):
    for letter in x[::-1]:
        print letter

which I think hits about the optimum between brevity and clarity. Your own 
optimum point may of course vary.