Re: [Tutor] Reading a Text File with tkFileDialog, askopenfilename+enumerate

Sun, 15 Feb 2009 12:30:03 -0800

Title: Signature.html
I don't think so. Not as a Python concept, but it looks sensible in your example. However, why would enumerate produce a line number? How would one know that it does? Ah, I see. enumerate produces a tuple which has the index and a list. It appears the only place this can be used is in a for?

And, of course (devoid of an example):
>>> help(enumerate)
class enumerate(object)
 |  enumerate(iterable) -> iterator for index, value of iterable
 | 
 |  Return an enumerate object.  iterable must be an other object that supports
 |  iteration.  The enumerate object yields pairs containing a count (from
 |  zero) and a value yielded by the iterable argument.  enumerate is useful
 |  for obtaining an indexed list: (0, seq[0]), (1, seq[1]), (2, seq[2]), ...
...
Kent Johnson wrote: 
On Sun, Feb 15, 2009 at 2:47 PM, Wayne Watson
<[email protected]> wrote:
  
I'm still looking for an explanation of "for (line_cnt, each_line) in
enumerate(input_file)". Why the tuple? Apparently, line_count gets a line
number, and each_line gets the string of text.
    

Do you know about sequence unpacking? In an assignment statement, when
the right side is a sequence, the left side can be a list of variables
of the same length as the sequence. Then each sequence element is
assigned to one variable. For example,

In [24]: item = (0, 'Spring')

In [25]: i, season = item

In [26]: i
Out[26]: 0

In [28]: season
Out[28]: 'Spring'

This can be used in a for loop, too, if the items are sequences. That
is what is commonly done with enumerate().

Kent

-- 
           Wayne Watson (Watson Adventures, Prop., Nevada City, CA)

             (121.01 Deg. W, 39.26 Deg. N) GMT-8 hr std. time)
            
            Shhhh, quiet. I'm thinking about filling this space. 



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