Below is a simple implementation of a FIFO in Python. My question is whether anything equivalent already exists in a maintained package, especially anything in the standard library, as it seems like a reasonably common thing to want to do. Functionality: you must be able to append to and iterate over it like a list, but when iteration yields an element, the internal reference to that element must be destroyed. Here is example of what I want to do with it: f = Fifo() # append to it for i in range(5): f.append(i) print("length:", len(f)) # iterate over it, including appending while iterating for i in f: print("item:", i) if i == 3: f.append("something") print("all for now") # iterate again (maybe we didn't previously iterate fully, # or, as in this example, appended some more items afterwards) f.append("another thing") f.append("and another thing") print("length:", len(f)) for i in f: print("item:", i) to give: length: 5 item: 0 item: 1 item: 2 item: 3 item: 4 item: something all for now length: 2 item: another thing item: and another thing And here is my implementation. (This uses a dictionary. A marginally simpler but less efficient alternative uses a list internally.) class Fifo: def __init__(self): self._d = {} self._cur = 0 # next key to pop def __len__(self): return len(self._d) def append(self, v): self._d[self._cur + len(self._d)] = v def __next__(self): if self._d: v = self._d.pop(self._cur) self._cur += 1 return v else: raise StopIteration def __iter__(self): return self Continue reading...
