Is there a Python equivalent for C++ multiset?
Is there a Python equivalent for C++ multiset?
There isnt. See Pythons standard library – is there a module for balanced binary tree? for a general discussion of the equivalents of C++ tree containers (map, set, multimap, multiset) in Python.
The closest I can think of is to use a dictionary mapping integers to counts (also integers). However this doesnt get you the keys in order, so you cant search using lower_bound. An alternative is a to use an ordered list, as suggested by others already, maybe a list of (integer, count) tuples? If you only need to search after youve done all your insertions, you could use the dictionary as a temporary structure for construction, build the list after youve done all the insertions, then use the list for searching.
There are a couple implementations of sorted list data types which would fit your criteria. Two popular choices are SortedContainers and blist modules. Each of these modules provides a SortedList data type which automatically maintains the elements in sorted order and would allow for fast insertion and lower/upper bound lookups. Theres a performance comparison thats helpful too.
The equivalent code using the SortedList type from the SortedContainers module would be:
from sortedcontainers import SortedList
sl = SortedList()
# Start index of `x` values
start = sl.bisect_left(x)
# End index of `x` values
end = sl.bisect_right(x)
# Iterator for those values
iter(sl[start:end])
# Erase an element
del sl[start:end]
# Insert an element
sl.add(x)
# Iterate from lower bound
start = sl.bisect_left(x)
iter(sl[x] for x in range(start, len(sl)))
# Clear elements
sl.clear()
All of those operations should work efficiently on a sorted list data type.
Is there a Python equivalent for C++ multiset?
There are a couple of data-structures which come close.
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python collections:
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provided by django framework: