ndarray如何使用简单的函数，如x ** 2？(How does ndarray work with a simple function, like x**2?)

ndarray如何使用简单的函数，如x ** 2？(How does ndarray work with a simple function, like x**2?)

ndarray如何使用简单的函数，如x ** 2？ 我收到此错误：

arr = array([3,4,5]) f = lambda x: x**2 print f(arr) # works, but how? print f(3) # works print f([3,4,5]) # will not work #TypeError: unsupported operand type(s) for ** or pow(): 'list' and 'int' print f((3,4,5)) # will not work #TypeError: unsupported operand type(s) for ** or pow(): 'tuple' and 'int' >>>f(arr) #[ 9 16 25] >>>f(3) #9

最后...

class Info(object): def __init__(self,x): self.a = x< def __pow__(self,x): for i in xrange(len(self.a)): self.a[i]**=x return self a = Info([3,4]) f = lambda x:x**2 a = f(a) print a.a [9, 16]

How does ndarray work with a simple function, like x**2? I get this error:

arr = array([3,4,5]) f = lambda x: x**2 print f(arr) # works, but how? print f(3) # works print f([3,4,5]) # will not work #TypeError: unsupported operand type(s) for ** or pow(): 'list' and 'int' print f((3,4,5)) # will not work #TypeError: unsupported operand type(s) for ** or pow(): 'tuple' and 'int' >>>f(arr) #[ 9 16 25] >>>f(3) #9

finally...

class Info(object): def __init__(self,x): self.a = x< def __pow__(self,x): for i in xrange(len(self.a)): self.a[i]**=x return self a = Info([3,4]) f = lambda x:x**2 a = f(a) print a.a [9, 16]

最满意答案

因为ndarray定义了 **运算符的行为 ，而列表元组则没有（它们可能包含任何对象，而ndarray通常用于数字）。

Because ndarray defines the behaviour for ** operator, whereas lists an tuples don't (they may contain whatever objects, whereas ndarrays are typically for numbers).