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I'm trying to find a way to write a combination function. Where can I find it?
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Using recursion. To create combinations without using itertools, iterate the list one by one and fix the first element of the list and make combinations with the remaining list. Similarly, iterate with all the list elements one by one by recursion of the remaining list.
To calculate the combinations of a dictionary in Python, use the itertools. combinations() method. The combinations() method takes a dictionary as an argument and returns all the possible combinations of the dictionary elements.
itertools. combinations (iterable, r) Return r length subsequences of elements from the input iterable. The combination tuples are emitted in lexicographic ordering according to the order of the input iterable. So, if the input iterable is sorted, the combination tuples will be produced in sorted order.
The actual source code is written in C and can be found in the file itertoolsmodule.c.
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See in the documentation of itertools.combinations. There is an equivalent code for this function:
def combinations(iterable, r): # combinations('ABCD', 2) --> AB AC AD BC BD CD # combinations(range(4), 3) --> 012 013 023 123 pool = tuple(iterable) n = len(pool) if r > n: return indices = range(r) yield tuple(pool[i] for i in indices) while True: for i in reversed(range(r)): if indices[i] != i + n - r: break else: return indices[i] += 1 for j in range(i+1, r): indices[j] = indices[j-1] + 1 yield tuple(pool[i] for i in indices) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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