Re: interating over single element array
Thank you both for clearing that up. -Basilisk96 -- http://mail.python.org/mailman/listinfo/python-list
Re: interating over single element array
"Basilisk96" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] | "Terry Reedy" <[EMAIL PROTECTED]> wrote: | > Any what if 'filelist' is any iterable other than a string or list? Your | > code is broken, and unnecessarily so. So I would call the parameter | > 'files' and test for isinstance(files, str) #or basestring. And wrap if it | > is. | | Can you give an example of such an iterable (other than a tuple)? Tuple was the first thing I thought of, and one will break the list test. The next would be an iterator that walks a file hierarchy spitting out the names of non-directory files, or all files with a certain extension, or all files with a certain owner, or timestamp characteristic. | I'd certainly like to fix my 'fix' to work for a more general case. As I said, I think it as simple as changing 'not list' to 'is string'. tjr -- http://mail.python.org/mailman/listinfo/python-list
Re: interating over single element array
In <[EMAIL PROTECTED]>, Basilisk96
wrote:
> "Terry Reedy" <[EMAIL PROTECTED]> wrote:
>> Any what if 'filelist' is any iterable other than a string or list? Your
>> code is broken, and unnecessarily so. So I would call the parameter
>> 'files' and test for isinstance(files, str) #or basestring. And wrap if it
>> is.
>
> Can you give an example of such an iterable (other than a tuple)? I'd
> certainly like to fix my 'fix' to work for a more general case.
def iter_filenames(filename):
lines = open(filename, 'r')
for line in lines:
yield line.rstrip()
lines.close()
filenames = iter_filenames('files.txt')
Now `filenames` is an iterable over strings representing file names but
it's not a `list`. And it's easy to come up with iterables over strings
that produce the data themselves, for example by attaching a counter to a
basename, or extracting the names from XML files, fetching them from a
database etc.
Ciao,
Marc 'BlackJack' Rintsch
--
http://mail.python.org/mailman/listinfo/python-list
Re: interating over single element array
"Terry Reedy" <[EMAIL PROTECTED]> wrote: > Any what if 'filelist' is any iterable other than a string or list? Your > code is broken, and unnecessarily so. So I would call the parameter > 'files' and test for isinstance(files, str) #or basestring. And wrap if it > is. Can you give an example of such an iterable (other than a tuple)? I'd certainly like to fix my 'fix' to work for a more general case. Regards, -Basilisk96 -- http://mail.python.org/mailman/listinfo/python-list
Re: interating over single element array
"Basilisk96" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] | On Jun 8, 11:54 am, "T. Crane" <[EMAIL PROTECTED]> wrote: | You can also do this (if tuples are okay in your case): | | a = 1, | | The comma turns 'a' into a tuple (1,) which is both iterable and has a | length of 1. | | I have run into this issue before with a function that took a list of | filenames (strings), and needed to iterate over the list to operate on | the input files. For the case when the input would be a single file, I | needed to turn the input string into an iterable such that the 'for' | loop would not iterate on the filename characters (a rather | undesirable gotcha, you understand :-) ). So I solved my problem like | this: | | def loadfiles(filelist): |if not isinstance(filelist, list): | filelist = filelist, Any what if 'filelist' is any iterable other than a string or list? Your code is broken, and unnecessarily so. So I would call the parameter 'files' and test for isinstance(files, str) #or basestring. And wrap if it is. |for filename in filelist: | f = open(filename,'r') | #do interesting stuff with file, etc... | | ..and it's been working very well. | | Cheers, | -Basilisk96 | | -- | http://mail.python.org/mailman/listinfo/python-list | -- http://mail.python.org/mailman/listinfo/python-list
Re: interating over single element array
On Jun 8, 11:54 am, "T. Crane" <[EMAIL PROTECTED]> wrote: > >> any suggestions are appreciated, > > > Yes, don't try iterating over objects that are not iterable. ;-) > > Ah, yes... I hadn't thought of that :) > > thanks, > trevis > > > > > What you *can* do is iterating over lists, tuples or other iterables with > > just one element in them. Try ``a = [1]``. > > > Ciao, > > Marc 'BlackJack' Rintsch You can also do this (if tuples are okay in your case): a = 1, The comma turns 'a' into a tuple (1,) which is both iterable and has a length of 1. I have run into this issue before with a function that took a list of filenames (strings), and needed to iterate over the list to operate on the input files. For the case when the input would be a single file, I needed to turn the input string into an iterable such that the 'for' loop would not iterate on the filename characters (a rather undesirable gotcha, you understand :-) ). So I solved my problem like this: def loadfiles(filelist): if not isinstance(filelist, list): filelist = filelist, for filename in filelist: f = open(filename,'r') #do interesting stuff with file, etc... ..and it's been working very well. Cheers, -Basilisk96 -- http://mail.python.org/mailman/listinfo/python-list
Re: interating over single element array
> >> any suggestions are appreciated, > > Yes, don't try iterating over objects that are not iterable. ;-) Ah, yes... I hadn't thought of that :) thanks, trevis > > What you *can* do is iterating over lists, tuples or other iterables with > just one element in them. Try ``a = [1]``. > > Ciao, > Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: interating over single element array
In <[EMAIL PROTECTED]>, T. Crane wrote: > Can someone please explain to me why I can't do something like this: > > a = 1 > > for value in a: > print str(value) > > If I run this I get the error: > > 'int' object is not iterable Well the message explains why you can't do this. `a` is bound to an integer and integers are not iterable. > Obivously this is an absurd example that I would never do, but in my > application the length of 'a' can be anything greater than 0, and I want to > be able to handle cases when 'a' has only one element without coding a > special case just in the event that len(a) = 1. ``len(a)`` wouldn't work either because integers have no "length": In [16]: a = 1 In [17]: len(a) --- exceptions.TypeError Traceback (most recent call last) /home/new/ TypeError: len() of unsized object > any suggestions are appreciated, Yes, don't try iterating over objects that are not iterable. ;-) What you *can* do is iterating over lists, tuples or other iterables with just one element in them. Try ``a = [1]``. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
interating over single element array
Hi all, Can someone please explain to me why I can't do something like this: a = 1 for value in a: print str(value) If I run this I get the error: 'int' object is not iterable Obivously this is an absurd example that I would never do, but in my application the length of 'a' can be anything greater than 0, and I want to be able to handle cases when 'a' has only one element without coding a special case just in the event that len(a) = 1. any suggestions are appreciated, trevis -- http://mail.python.org/mailman/listinfo/python-list
