| |
| |
| class LookAheadIterator(object): |
| def __init__(self, iterable): |
| self.iterable = iter(iterable) |
| self.look_ahead = list() |
| self.markers = list() |
| self.default = None |
| self.value = None |
| |
| def __iter__(self): |
| return self |
| |
| def set_default(self, value): |
| self.default = value |
| |
| def next(self): |
| return self.__next__() |
| |
| def __next__(self): |
| if self.look_ahead: |
| self.value = self.look_ahead.pop(0) |
| else: |
| self.value = next(self.iterable) |
| |
| if self.markers: |
| self.markers[-1].append(self.value) |
| |
| return self.value |
| |
| def look(self, i=0): |
| """ Look ahead of the iterable by some number of values with advancing |
| past them. |
| |
| If the requested look ahead is past the end of the iterable then None is |
| returned. |
| |
| """ |
| |
| length = len(self.look_ahead) |
| |
| if length <= i: |
| try: |
| self.look_ahead.extend([next(self.iterable) |
| for _ in range(length, i + 1)]) |
| except StopIteration: |
| return self.default |
| |
| self.value = self.look_ahead[i] |
| return self.value |
| |
| def last(self): |
| return self.value |
| |
| def __enter__(self): |
| self.push_marker() |
| return self |
| |
| def __exit__(self, exc_type, exc_val, exc_tb): |
| # Reset the iterator if there was an error |
| if exc_type or exc_val or exc_tb: |
| self.pop_marker(True) |
| else: |
| self.pop_marker(False) |
| |
| def push_marker(self): |
| """ Push a marker on to the marker stack """ |
| self.markers.append(list()) |
| |
| def pop_marker(self, reset): |
| """ Pop a marker off of the marker stack. If reset is True then the |
| iterator will be returned to the state it was in before the |
| corresponding call to push_marker(). |
| |
| """ |
| |
| marker = self.markers.pop() |
| |
| if reset: |
| # Make the values available to be read again |
| marker.extend(self.look_ahead) |
| self.look_ahead = marker |
| elif self.markers: |
| # Otherwise, reassign the values to the top marker |
| self.markers[-1].extend(marker) |
| else: |
| # If there are not more markers in the stack then discard the values |
| pass |
| |
| class LookAheadListIterator(object): |
| def __init__(self, iterable): |
| self.list = list(iterable) |
| |
| self.marker = 0 |
| self.saved_markers = [] |
| |
| self.default = None |
| self.value = None |
| |
| def __iter__(self): |
| return self |
| |
| def set_default(self, value): |
| self.default = value |
| |
| def next(self): |
| return self.__next__() |
| |
| def __next__(self): |
| try: |
| self.value = self.list[self.marker] |
| self.marker += 1 |
| except IndexError: |
| raise StopIteration() |
| |
| return self.value |
| |
| def look(self, i=0): |
| """ Look ahead of the iterable by some number of values with advancing |
| past them. |
| |
| If the requested look ahead is past the end of the iterable then None is |
| returned. |
| |
| """ |
| |
| try: |
| self.value = self.list[self.marker + i] |
| except IndexError: |
| return self.default |
| |
| return self.value |
| |
| def last(self): |
| return self.value |
| |
| def __enter__(self): |
| self.push_marker() |
| return self |
| |
| def __exit__(self, exc_type, exc_val, exc_tb): |
| # Reset the iterator if there was an error |
| if exc_type or exc_val or exc_tb: |
| self.pop_marker(True) |
| else: |
| self.pop_marker(False) |
| |
| def push_marker(self): |
| """ Push a marker on to the marker stack """ |
| self.saved_markers.append(self.marker) |
| |
| def pop_marker(self, reset): |
| """ Pop a marker off of the marker stack. If reset is True then the |
| iterator will be returned to the state it was in before the |
| corresponding call to push_marker(). |
| |
| """ |
| |
| saved = self.saved_markers.pop() |
| |
| if reset: |
| self.marker = saved |
| elif self.saved_markers: |
| self.saved_markers[-1] = saved |
| |
