It feels so good, so quick and not C!

[Roy Smith]

In article <mailman.1047952113.6728.python-list at python.org>,
 "BB" <bbondi at pacbell.net> wrote:

> Hi ya'all
>   I've been lurking and learning as much as I can. I then decided to do a
> simple project to write a "reverse string" routine. This helped a lot! It
> showed me that I really think in C terms. I am beginning to see the value of
> lists and the simplicity they bring to manipulation of data.
>   Anyway, I throwing this piece of code into the arena to be kicked about -
> I hope to learn even more this way.
> 
> print "This is a prompt. Enter a string to be reversed: ",
> sOrig = raw_input()#get a string to work on
> sRev=""#init
> char_count=len(sOrig)#now I have the string length
> while ((char_count - 1) >= 0):#loop thru string backwards, zero based
>    char_count = char_count - 1
>    sRev = sRev+sOrig[char_count]#create the reverse string
> print sRev
> 
> 

While what you've written will probably work (I'll confess, I havn't run 
it myself to make sure), it is a very C-like way of doing things.  In 
general, anytime in Python you find yourself walking through a sequence 
by incrementing an index, you should suspect you're doing something in 
an "un-pythonic" way.

I've fallen into that trap more than once, and each time, after I've 
recognized the problem and rewritten it pythonicly, I've ended up with 
more readable (and often, faster executing) code.

Ignoring for the moment convenient built-ins like reverse(), I'd be 
thinking more along the lines of:

reverseList = []               # create an empty list
for c in sOrig:                # walk the string, one char at a time
   reverseList.insert (0, c)   # pushes c onto front of reverseList

sRev = ''.join(reverseList)    # squashes list of characters into string
print sRev