Python3中省略号(...)用法介绍

本文主要介绍了Python3中省略号(...)用法介绍,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友们下面随着小编来一起学习学习吧

1. 省略号(...)是一个Python对象,叫Ellipsis,它没有方法,是一个单例对象(singleton object):

# 1. ...是一个python对象,叫Ellipsis print(type(...)) # output:  print(...) # output: Ellipsis print(Ellipsis) #  output: Ellipsis print(bool(...)) # output: True

2. 它可用作Python解释器中的默认辅助提示符(default secondary prompt):

3. 它用于访问和切片(accessing and slicing)多维数组/NumPy索引,注:不能在一个切片中有多个省略号

# 3. slice: we can not have multiple ellipsis in a single slicing array = np.random.rand(2, 4) # a 2-dimensional matrix of order 2*4(rows*cols) print(array); print(array[...]); print(array[Ellipsis]) # they are all equivalent print(array[..., 0]); print(array[:,0]); print(array[Ellipsis, 0]) # they are all equivalent print(array[0, ...])

4. 它可用在类型提示中(in type hinting):

# 4. type hints # 当函数的参数类型允许为Any def inject(get_next_item: Callable[..., str]) -> None: ... def foo(x: ...) -> None: ... # 当函数的返回类型为Any class flow: def __understand__(self, name: str, value: ...) -> None: ...

5. 它可用作函数内部的pass语句:

# 5. used as Pass Statement inside Functions # foo1 and foo2 styles are same def foo1(): pass def foo2(): ...

6. 它可用作默认参数值:

# 6. used as a default argument value def foo3(x = ...): return x def foo4(x = None): return x print("foo3:", foo3) # output: foo3:  print("foo4:", foo4) # output: foo4: 

GitHubhttps://github.com/fengbingchun/Python_Test

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