can add int to float but can't add float to int

Question

import numpy as np
a = np.full((2,3),3, dtype=int)
print(a)
print(a.dtype.name) #int32
b = np.random.random((2,3))
print(b) #float64
print(b.dtype.name)

b += a #this works
print(b)

a += b #this doesnt work
print(a)

#error message
TypeError Traceback (most recent call last)
<ipython-input-44-ab0d7ebed8b7> in <module>
10 print(b)
11
---> 12 a += b
13 print(a)
14

TypeError: Cannot cast ufunc add output from dtype('float64') to dtype('int32') with casting rule 'same_kind'

"""
I don't understand, I can add int to float but can't do the reverse
"""

Answer 1

They may look similar, but they are treated differently.

"The += operator preserves the type of the array. In other words, an array of integers remains an array of integers.

[...] On the other hand, a=a+b creates a brand new array for the sum, and rebinds a to point to this new array".

https://stackoverflow.com/a/10740003

Answer 2

Diego Understood thanks

Answer 3

a = a+b

Answer 4

this is because Python implicitly (behind the scenes) converts the int to a float whenever a float is used in the code.
just like / (division) makes an int a float. 9+3=12 but 9/3=3.0

this “secret” conversion doesn’t work the other way around.

Answer 5

Brave Tea thanks for the insight and Diego a = a+b works. But its confusing coz a += b means the same thing as a = a+b, so why should one work and the other not work. thanks