Calling a lambda with a numpy array

Its all about Overriding operators in numpy

You can learn numpy.arry here

Let us focus on your lamda function for each;

1. numpy array :

arr = numpy.array([1, 2, 3])
type(arr)
scale = lambda x: x * 3 
scale(arr)

this takes each element from array

2. normal list:

a =[1,2,3]
type(a)
scale = lambda x: x * 3 
scale(a)

this takes full list as x and multiplies the list here itself

numpy.ndarray overloads the * operator by defining its own __mul__ method. Likewise for +, -, etc. This allows for vector arithmetic.

These are two different objects which behaves differently when you use * operator on them.

In the first case you generate a numpy array. In this case, * operator was overloaded for performing multiplication. i.e. every element will be multiplied by 3.
In the second case you generate a list. In this case the * operator is treated as a repetition operator, and the entire list is repeated 3 times.

code example:

type(np.array([1,2,3]))
type([1, 2, 3])

result:

numpy.ndarray
list

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