纯python代码实现一个range函数

源代码:

class MyRange:

    def __init__(self, start, stop=None, step=None):

        # 模拟range从0开始的行为
        if stop is None:
            self.start = 0
            self.stop = start - 1
        else:
            self.start = start
            self.stop = stop - 1

        self.step = step

        # 保留原始参数
        self.origin_start = self.start
        self.origin_stop = self.stop + 1
        self.origin_step = self.step

    def __repr__(self):
        """
        :return: 显示表现
        """
        if self.origin_step:
            result = '{}({}, {}, {})'.format(
                self.__class__.__name__,
                self.origin_start,
                self.origin_stop,
                self.origin_step
            )
        else:
            result = '{}({}, {})'.format(
                self.__class__.__name__,
                self.origin_start,
                self.origin_stop
            )
        return result

    def __iter__(self):
        return self

    def __next__(self):
        """
        :return: 返回当前数字，然后在当前数字上+1
        """
        result = self.start
        if self.start <= self.stop:
            self.start += 1
        else:
            raise StopIteration

        return result

    def __getitem__(self, item):
        """
        :param item: 如果是单个数字, 那么item的类型将会是int,
                      如果是分片那么item将会是一个slice.
        :return: 返回分片结果
        """

        def is_index_error(_start):
            if _start > self.stop:
                raise IndexError('分片不得大于最大值.')

        if isinstance(item, int):
            result = self.origin_start + item
            is_index_error(result)
        elif isinstance(item, slice):
            start = self.origin_start + item.start
            stop = self.origin_start + item.stop
            list(map(is_index_error, MyRange(start, stop)))
            result = MyRange(start, stop)
        else:
            raise KeyError

        return result

 
 

打印类对象信息

print(range(10), MyRange(10), sep=' ' * 10)
print(range(10, 20), MyRange(10, 20), sep=' ' * 10)

# 显示结果
range(0, 10)          MyRange(0, 10)
range(10, 20)          MyRange(10, 20)

 
 

打印单个分片信息

print(range(10)[4], MyRange(10)[4], sep=' ' * 10)
# 显示结果
4          4

 
 

打印一组分片信息

print(range(10)[5:8], MyRange(10)[5:8], sep=' ' * 10)
# 显示结果
range(5, 8)          MyRange(5, 8)

 
 

循环迭代

for i in range(10):
    print('range: ', i)

print('\n')

for i in MyRange(10):
    print('MyRange: ', i)
    
# 显示结果
range:  0
range:  1
range:  2
range:  3
range:  4
range:  5
range:  6
range:  7
range:  8
range:  9


MyRange:  0
MyRange:  1
MyRange:  2
MyRange:  3
MyRange:  4
MyRange:  5
MyRange:  6
MyRange:  7
MyRange:  8
MyRange:  9

 
 

异常处理

s = MyRange(10)
print(s[15])

# 显示结果
Traceback (most recent call last):
    File "XXXXXXXX.py", line 117, in <module>
    File "XXXXXXXX.py", line 69, in __getitem__
    File "XXXXXXXX.py", line 65, in is_index_error
IndexError: 分片不得大于最大值.