[Python-ideas] pipe function for itertools?

Donald 'Paddy' McCarthy paddy3118 at gmail.com
Tue May 26 12:32:58 CEST 2009

Hi, I have a blog entry, http://paddy3118.blogspot.com/2009/05/pipe-fitting-with-python-generators.html,
in which I define a helper function to get around the problem of
reversion in the nesting of generators and the proliferation of nested

See the blog entry for a fuller treatment, but in essence if you have
a series of generators, and want the data to conceptually flow like

gen1 -> gen2 -> gen3 -> gen4 ...

You have to write:


With pipe, you would write:

pipe(gen1, gen2, gen3, gen4, ...)

Which you could use like this:

for data in pipe(...): do_something_with_data()

If I use dots for indentation, then maybe the definition will come
through to the group:

def pipe(*cmds):
....gen = cmds[0]
....for cmd in cmds[1:]:
....... gen = cmd(gen)
....for x in gen:
....... yield x

A couple of readers thought that it might be a good tool for itertools
to have. There are other solutions out there that use classes to
overload '|', or, but it seems more natural to me to use pipe(), even
though I am a heavy Unix user.

Please discuss.

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