- vs -= operators with numpy

Question

I\'m having some strange behavior in my python code related to - and -=. I\'m writing a QR decomposition using numpy, and have the following line o

Answer 1

+1 to both other answers to this questions. They cover two important differences between = and -= but I wanted to highlight one more. Most of the time x -= y is the same as x[:] = x - y, but not when x and y are slices of the same array. For example:

x = np.ones(10)
y = np.ones(10)

x[1:] += x[:-1]
print x
[  1.   2.   3.   4.   5.   6.   7.   8.   9.  10.]

y[1:] = y[1:] + y[:-1]
print y
[ 1.  2.  2.  2.  2.  2.  2.  2.  2.  2.]