实现range类
本帖最后由 KeyError 于 2023-1-17 17:18 编辑>>> #shell
>>> help(range)
Help on class range in module builtins:
class range(object)
|range(stop) -> range object
|range(start, stop[, step]) -> range object
|
|Return an object that produces a sequence of integers from start (inclusive)
|to stop (exclusive) by step.range(i, j) produces i, i+1, i+2, ..., j-1.
|start defaults to 0, and stop is omitted!range(4) produces 0, 1, 2, 3.
|These are exactly the valid indices for a list of 4 elements.
|When step is given, it specifies the increment (or decrement).
|
|Methods defined here:
|
|__bool__(self, /)
| self != 0
|
|__contains__(self, key, /)
| Return key in self.
|
|__eq__(self, value, /)
| Return self==value.
|
|__ge__(self, value, /)
| Return self>=value.
|
|__getattribute__(self, name, /)
| Return getattr(self, name).
|
|__getitem__(self, key, /)
| Return self.
|
|__gt__(self, value, /)
| Return self>value.
|
|__hash__(self, /)
| Return hash(self).
|
|__iter__(self, /)
| Implement iter(self).
|
|__le__(self, value, /)
| Return self<=value.
|
|__len__(self, /)
| Return len(self).
|
|__lt__(self, value, /)
| Return self<value.
|
|__ne__(self, value, /)
| Return self!=value.
|
|__reduce__(...)
| Helper for pickle.
|
|__repr__(self, /)
| Return repr(self).
|
|__reversed__(...)
| Return a reverse iterator.
|
|count(...)
| rangeobject.count(value) -> integer -- return number of occurrences of value
|
|index(...)
| rangeobject.index(value) -> integer -- return index of value.
| Raise ValueError if the value is not present.
|
|----------------------------------------------------------------------
|Static methods defined here:
|
|__new__(*args, **kwargs) from builtins.type
| Create and return a new object.See help(type) for accurate signature.
|
|----------------------------------------------------------------------
|Data descriptors defined here:
|
|start
|
|step
|
|stop
>>>
所以，我们今天来实现range类的基本功能{:10_298:}
根据小甲鱼老师的生成器，代码显而易见
>>> class range:
def __init__(self, stop, /):
self.stop = stop
self.num = -1
def __iter__(self):
return self
def __next__(self):
self.num += 1
if self.num >= self.stop:
raise StopIteration
return self.num
>>>
但是这样并不能传入开始值和步长{:10_249:}
问题是如果只有一个参数，它应该是结束值，但有两个及以上，应该按开始值，结束值，步长的顺序传入。
两千年后，我终于想到了办法！
class range:
def __init__(self, *args, /):
if len(args) == 1:
self.stop = args
self.num = -1
self.add = 1
elif len(args) == 2:
self.stop = args
self.num = args - 1
self.add = 1
elif len(args) == 3:
self.stop = args
self.num = args - 1
self.add = args
elif len(args) == 0:
raise TypeError("range expected at 1 argument, got 0")
else:
raise TypeError(f"range expexct ed at 3 argument, got {len(args)}")
def __iter__(self):
return self
def __next__(self):
self.num += self.add
if self.num >= self.stop:
raise StopIteration
return self.num
>>>
>>> for i in range(1, 10, 2):
print(i)
1
3
5
7
9
>>>
完美！{:10_279:}
{:5_106:}
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