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I always tend to recommend intermediate/advanced programmers to take a look at `functools` and `collections` packages - they are filled with amazing things that

I always tend to recommend intermediate/advanced programmers to take a look at `functools` and `collections` packages - they are filled with amazing things that you haven't even though you need! My favourites are `functools.partial`, `collections.Counter` and `collections.defaultdict` that are used very often by people who are aware of their existance.

ehsankia 7y ago
I use defaultdict so damn often, it honestly should even be a builtin in my opinion. You also forgot `itertools`, which imo is even more useful than `functools`. I use `chain` and `groupby` quite often. There's also `collections.deque` which is a quick linked list implementation if you need either a stack or a queue.
- abhishekjha 7y ago
  Forgive me doesn’t deque mean double ended queue? Also why can’t a simple array behave like a list?
  - tehnub 7y ago
    Yes it does mean double ended queue. I'll assume you mean a python list when you say simple array. One drawback of lists is that you cannot add a new element to the start of a list in constant time (with a python list it requires O(n) time), whereas you can with a deque.
    - nathanasmith 7y ago
      I had a script a while back that created really long lists at runtime by continually appending data as it came over the wire. The lists would quickly get so long that I needed to remove items from the beginning to conserve memory though because reasons I could only remove items one at a time. Long story short, converting those lists to collections.deque and making use of popleft() rather than "del l[0]" improved performance considerably.
  - ehsankia 7y ago
    Normal lists have a backing array. In theory, every time you resize it, it needs to allocate new memory and copy everything over, which is very slow. Obviously python does a lot of optimization behind the scene by over-allocating memory, which gives it better amortized speed. Linked lists are slow at accessing data in the middle, but you can very quickly add and remove stuff from the ends, hence double-ended queue. A stack is basically a deque where you only use the tip, so deque is very versatile like that.
abhishekjha 7y ago
I have been using defaultdict and Counter a lot lately, not much partial though. Also sets are another nice thing about python.
radarsat1 7y ago
Also `itertools.product` is very useful to avoid nested for-loops.

ehsankia 7y ago

I use defaultdict so damn often, it honestly should even be a builtin in my opinion. You also forgot `itertools`, which imo is even more useful than `functools`. I use `chain` and `groupby` quite often. There's also `collections.deque` which is a quick linked list implementation if you need either a stack or a queue.

abhishekjha 7y ago
Forgive me doesn’t deque mean double ended queue? Also why can’t a simple array behave like a list?
- tehnub 7y ago
  Yes it does mean double ended queue. I'll assume you mean a python list when you say simple array. One drawback of lists is that you cannot add a new element to the start of a list in constant time (with a python list it requires O(n) time), whereas you can with a deque.
  - nathanasmith 7y ago
    I had a script a while back that created really long lists at runtime by continually appending data as it came over the wire. The lists would quickly get so long that I needed to remove items from the beginning to conserve memory though because reasons I could only remove items one at a time. Long story short, converting those lists to collections.deque and making use of popleft() rather than "del l[0]" improved performance considerably.
- ehsankia 7y ago
  Normal lists have a backing array. In theory, every time you resize it, it needs to allocate new memory and copy everything over, which is very slow. Obviously python does a lot of optimization behind the scene by over-allocating memory, which gives it better amortized speed. Linked lists are slow at accessing data in the middle, but you can very quickly add and remove stuff from the ends, hence double-ended queue. A stack is basically a deque where you only use the tip, so deque is very versatile like that.

abhishekjha 7y ago

I have been using defaultdict and Counter a lot lately, not much partial though. Also sets are another nice thing about python.

radarsat1 7y ago

Also `itertools.product` is very useful to avoid nested for-loops.