A look at some of Python's useful itertools
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A look at some of Python's useful itertools
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Re: A look at some of Python's useful itertools
#2My intention is not to be snarky, but people post all the time about discovering the itertools or collections library. I notice it's a common gap in newer Python programmers.
Save yourself time and effort down the road and read through both libraries' documentation, they're well worth the effort:
http://docs.python.org/3.3/library/itertools.html
http://docs.python.org/3.3/library/collections.html
I tend to use defaultdict, deque (thread safe), namedtuple, imap, izip, drop/takewhile. In Python 3, map and zip have been replaced with their itertools equivalents.
I blame Haskell for all the lazy evaluation influence. :P
Re: A look at some of Python's useful itertools
#3My intention is not to be snarky, but people post all the time about discovering the itertools or collections library. I notice it's a common gap in newer Python programmers. Save yourself time and effort down the road and read through both libraries' documentation, they're well worth the effort: http://docs.python.org/3.3/library/itertools.html http://docs.python.org/3.3/library/collections.html I tend to use defaul…
Author here. I completely agree with you. Could have known all this before had I just read the itertools docs beyond permutations and combinations. It was only after using Scala's groupby while solving an assignment problem that I thought about finding out an equivalent in python. And thanks to having worked with the Stream class from Scala collections, for the first time the rest of the itertools also made sense. Better late than never I guess :-)
Re: A look at some of Python's useful itertools
#4 def flatmap(f, items):
return itertools.chain(*map(f, items))
2. it's being eagerly unpacked through *, itertools.chain also provides a from_iterable method which doesn't have that issue (and can be used to flatten infinite streams), introduced in 2.6
So `flatmap` would probably be better as:
def flatmap(f, items):
return itertools.chain.from_iterable(
itertools.imap(
f, items))Re: A look at some of Python's useful itertools
#5My intention is not to be snarky, but people post all the time about discovering the itertools or collections library. I notice it's a common gap in newer Python programmers. Save yourself time and effort down the road and read through both libraries' documentation, they're well worth the effort: http://docs.python.org/3.3/library/itertools.html http://docs.python.org/3.3/library/collections.html I tend to use defaul…
Author here. I completely agree with you. Could have known all this before had I just read the itertools docs beyond permutations and combinations. It was only after using Scala's groupby while solving an assignment problem that I thought about finding out an equivalent in python. And thanks to having worked with the Stream class from Scala collections, for the first time the rest of the itertools also made sense. Be…
Is there any reason that you don't switch over to Scala for your main programming language?
I'm in the process of converting a middle-sized PHP codebase completely over to Scala. It is not uncommon for me to see functions that run between 15 and 30 lines shrink to 3 or 4 line functions thanks to the Collections API. On top of that its performance is something you'll never see in PHP or Python. I love Python for its readability and wonderful syntax, but Scala is starting to have an even greater pull on me for its built in concision and the ability to use the entire Java ecosystem without submitting to java's imperative style.
Re: A look at some of Python's useful itertools
#6I wrote my favorite function ever last semester with itertools! It (roughly) lazily generates a list of dictionaries that map players to their moves for all possible moves. It turns out you can do that with a chain of combinations, two cartesian products, and an imap: https://github.com/shargoj/acquire/blob/master/gametree.py#L...
Re: A look at some of Python's useful itertools
#7My intention is not to be snarky, but people post all the time about discovering the itertools or collections library. I notice it's a common gap in newer Python programmers. Save yourself time and effort down the road and read through both libraries' documentation, they're well worth the effort: http://docs.python.org/3.3/library/itertools.html http://docs.python.org/3.3/library/collections.html I tend to use defaul…
>My intention is not to be snarky, but people post all the time about discovering the itertools or collections library. I notice it's a common gap in newer Python programmers.
Not only in Python, but programming languages in general.
I still find people writing Java or .NET code that aren't aware of all nice classes that are part of the runtime and end up creating their half baked solutions for their problems.
Nowadays developers seem to code without reading.
Re: A look at some of Python's useful itertools
#8def flatmap(f, items): return itertools.chain(*map(f, items)) 1. in Python 2 `map` is eager which — as with the previous `even` filter — may lead to unnecessary work if you only need part of the list (or a dead process if the input is infinite...). itertools.imap (or a generator comprehension) would be better. This is "fixed" in Python 3 (where the `map` builtin has become lazy and `itertools.imap` has been removed)…
Thanks for the corrections. I have made an edit (although not sure how long it will take to clear the github-pages cache)
Re: A look at some of Python's useful itertools
#9Earlier quoted context omitted.
Author here. I completely agree with you. Could have known all this before had I just read the itertools docs beyond permutations and combinations. It was only after using Scala's groupby while solving an assignment problem that I thought about finding out an equivalent in python. And thanks to having worked with the Stream class from Scala collections, for the first time the rest of the itertools also made sense. Be…
Is there any reason that you don't switch over to Scala for your main programming language? I'm in the process of converting a middle-sized PHP codebase completely over to Scala. It is not uncommon for me to see functions that run between 15 and 30 lines shrink to 3 or 4 line functions thanks to the Collections API. On top of that its performance is something you'll never see in PHP or Python. I love Python for its r…
It's very tempting. Frankly, I had enrolled for the course mainly for functional programming and not Scala but towards the end I started liking it. But, at the moment my main languages at work are Python, Erlang and Javascript and I still have a long way to go with these so planning to stick to them for a while.
Re: A look at some of Python's useful itertools
#10My intention is not to be snarky, but people post all the time about discovering the itertools or collections library. I notice it's a common gap in newer Python programmers. Save yourself time and effort down the road and read through both libraries' documentation, they're well worth the effort: http://docs.python.org/3.3/library/itertools.html http://docs.python.org/3.3/library/collections.html I tend to use defaul…
>My intention is not to be snarky, but people post all the time about discovering the itertools or collections library. I notice it's a common gap in newer Python programmers. Not only in Python, but programming languages in general. I still find people writing Java or .NET code that aren't aware of all nice classes that are part of the runtime and end up creating their half baked solutions for their problems. Nowada…
Nowadays developers seem to code without reading.
When your standard library documentation is so vast that it would take weeks to read and understand it all, and you'd never remember most of it anyway without context and experience using it, I don't think "coding without reading" is really a fair complaint.
We as an industry need to get better at documentation, and in particular about separating tutorial/overview documentation that presents a map and summary of what's available from reference documentation, or we're going to keep reinventing wheels like this.
Python is a particularly unfortunate example, because while its documentation is vast, it has very little tutorial/overview material beyond the very basics. For example, given that a substantial proportion of Python's standard library actually doesn't work very well in practice, it would be helpful to have a deeper tutorial/map document somewhere that introduced the various areas of the standard library and that also promoted the good ones and suggested popular alternatives for the not so good ones where they exist.