Iterate over text file, discarding some lines via context manager

Dave Angel davea at davea.name
Fri Nov 28 18:40:38 CET 2014


Please don't start a new thread when responding to an existing topic. 
Just reply-List to the message you're responding to, and include some 
context from that message.

On 11/28/2014 12:06 PM, ast wrote:
> Hi
>
> Here is a solution with a custom iterator which operate on files.
> I tested it with a small file. Just a remark, there are no empty line
> on a file, there is at least '\n' at the end of each lines but maybe the
> last one. If readline() got an emptyline, then the end of file has been
> reached.
>
>
> class MyFileItr:
>     def __init__(self, f):
>         self.f = f
>         self.line = ""
>
>     def __next__(self):
>
>         while True:
>             self.line = self.f.readline()
>
>             if (self.line == ''):
>                 raise StopIteration
>             if not(self.line.startswith('#') or self.line.isspace() or
> self.line == '\n'):
>                 return self.line
>
>     def __iter__(self):
>         return self
>
>
> f = open('test.txt', 'r')
>
> for L in MyFileItr(f):
>     print(L, end="")
>

Why would you prefer that over a generator function, as given earlier in 
the thread?  See for example Ned's message.  By using 'yield', you get 
Python to generate all the class boilerplate for you.



-- 
DaveA



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