[Numpy-discussion] loop through values in a array and find maximum as looping

[questions anon]

I would like to produce an array with the maximum values out of many
(10000s) of arrays.
I need to loop through many multidimentional arrays and if a value is
larger (in the same place as the previous array) then I would like that
value to replace it.

e.g.
a=[1,1,2,2
11,2,2
1,1,2,2]
b=[1,1,3,2
2,1,0,0
1,1,2,0]

where b>a replace with value in b, so the new a should be :

a=[1,1,3,2]
2,1,2,2
1,1,2,2]

and then keep looping through many arrays and replace whenever value is
larger.

I have tried numpy.putmask but that results in
TypeError: putmask() argument 1 must be numpy.ndarray, not list
Any other ideas? Thanks
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