import numpy as np
# 等差数列
print(np.linspace(0.1, 1, 10, endpoint=True))
print(np.arange(0.1, 1.1, 0.1))
"""总结：
  arange 侧重点在于增量，不管产生多少个数
  linspace 侧重于num, 即要产生多少个元素，不在乎增量
"""
 
# 等比数列
np.logspace(1, 4, 4, endpoint=True, base=2) # 2**1---2**4

"""
等差数列实现。
"""


class ArithmeticProgression:

  def __init__(self, begin, step, end=None):
    self.begin = begin
    self.step = step
    self.end = end  # None -> 无穷数列

  def __iter__(self):
    result = type(self.begin + self.step)(self.begin)
    forever = self.end is None
    index = 0
    while forever or result < self.end:
      yield result
      index += 1
      result = self.begin + self.step * index


if __name__ == '__main__':
  ap = ArithmeticProgression(0, 1, 3)
  print(ap)
  # print(list(ap))
  a = iter(ap)
  print(next(a))

def aritprog_gen(begin, step, end=None):
  result = type(begin + step)(begin)
  forever = end is None
  index = 0
  while forever or result < end:
    yield result
    index += 1
    result = begin + step * index

import itertools 


# 注意，下面示例中的 aritprog_gen 不是生成器函数，
# 因为定义体中没有 yield 关键字。
# 但是它会返回一个生成器，
# 因此它与其他生成器函数一样，
# 也是生成器工厂函数。
def aritprog_two_gen(begin, step, end=None):
  first = type(begin + step)(begin)
  ap_gen = itertools.count(first, step)
  if end is not None:
    ap_gen = itertools.takewhile(lambda n: n < end, ap_gen)
  return ap_gen