Python3中省略号(...)用法介绍

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: <class 'ellipsis'>
print(...) # output: Ellipsis
print(Ellipsis) yhIBk#  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(ar编程客栈ray[Elli开发者_开发培训psis]) # 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python提示中(in type hinting)：

# 4. type hintwww.devze.coms
# 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: <function foo3 at 0x7f4e7ffcf5e0>
print("foo4:", foo4) # output: foo4: <function foo4 at 0x7f4e7ffcf550>

github：https://github.com/fengbingchun/Python_Test

到此这篇关于Pythonandroid3中省略号(...)用法介绍的文章就介绍到这了,更多相关Python3 省略号内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！