Re: [Tutor] understanding join
On 31/07/2008, Steve Poe [EMAIL PROTECTED] wrote:
Hi tutor list,
Just trying to add some clarity to the built-in function strings using
join. The Python help
screen says it returns a string which is a concatenation of strings in
sequence. I am concatenating
the string I am working on that maybe an issue of its own.
[...]
but if string is 'abc'
print string.join(string)
aabcbabcc
Hi Steve,
First up, a quick comment: There is a string module in the standard
library, and it has a function called join(). So it's generally a
good idea not to use 'string' as a variable name, as it can confuse
people :-)
Now, to your question: your string is 'abc'. It doesn't matter that
you're using a string to join itself; what you've written is identical
to:
'abc'.join('abc')
'aabcbabcc'
Let's change the call slightly to make things more clear:
'abc'.join('ABC')
'AabcBabcC'
Does that make the pattern more clear?
--
John.
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Re: [Tutor] understanding join
On 31/07/2008, Steve Poe [EMAIL PROTECTED] wrote:
Good point. I guess I am surprised a little that Python does not error
on that you cannot assign a variable to a module name. I know I need
to learn proper coding techniques.
Well, that wouldn't really work because you don't know what other
modules people have.
Okay, I can see the order of the join is the same as mine, but
the join still seems to be out of sequence. I am thinking it should be
'abcABC' or 'ABCabc' not at the beginning, middle, and end of the
original string. At least, I am trying to wrap my head around its
usefulness.
Say I have a sequence seq and a string s, and I call s.join(seq).
Here's what it does:
s.join(seq) == seq[0] + s + seq[1] + s + seq[2] + s + ... + seq[-2] +
s + seq[-1]
So if you call 'abc'.join('ABC'), you get:
'ABC'[0] + 'abc' + 'ABC'[1] + 'abc' + 'ABC'[2]
which is:
'A' + 'abc' + 'B' + 'abc' + 'C'
Hope this helps.
--
John.
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Re: [Tutor] understanding join
On 31/07/2008, Steve Poe [EMAIL PROTECTED] wrote: Okay, I can see the order of the join is the same as mine, but the join still seems to be out of sequence. I am thinking it should be 'abcABC' or 'ABCabc' not at the beginning, middle, and end of the original string. At least, I am trying to wrap my head around its usefulness. Does this look useful? In [3]: people = [ 'Tom', 'Dick', 'Harry' ] In [4]: ', '.join(people) Out[4]: 'Tom, Dick, Harry' Your confusion is in thinking about the string 'ABC' as a single entity. For the purposes of join(), it is a sequence of three letters. The argument to join() is a sequence of strings, not a single string. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] understanding join
Steve Poe [EMAIL PROTECTED] wrote Your explanation is very help. It does make be wonder the usefulness of join with strings. Do you have a practical example/situation? Its not really intended for strings but it needs to work that way to be consistent because strings are just another type of collection in Python and we want to treat collections (or sequences) as consistently as possible. But there are times when you want to separate the characters of a string out for display and inserting a space or a comma using join is convenient. It would be extremely rare to use mystring.joing(mystring) It is usually myseparator.join(mysequence) HTH -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
