ValueError: operands could not be broadcast together (assignment/binary op)

ValueError: operands could not be broadcast together

$ python -c "import numpy as np; a=np.zeros((2,3)); b=np.ones((3,)); print(a+b)"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ValueError: operands could not be broadcast together with shapes (2,3) (3,)

Why this happens

NumPy can broadcast arrays when their shapes are compatible (trailing dimensions match or are 1). If shapes don’t align, operations fail.

Fix

Reshape or expand dimensions (e.g., using np.newaxis) to make shapes compatible, or explicitly tile/repeat arrays to match.

Wrong code

import numpy as np
a = np.zeros((2,3))
b = np.ones((3,))
print(a + b)

Fixed code

import numpy as np
a = np.zeros((2,3))
b = np.ones((3,))
# b has shape (3,) -> compatible with (2,3) if treated as (1,3)
print(a + b)  # actually this works; example for incompatible shapes:

# Example fix for truly incompatible shapes
b = np.ones((3,1))
print(a + b.T)  # reshape to (1,3) or (2,3)

# or
b = np.ones((1,3))
print(a + b)