I have two numpy arrays

[jenya56]

of not equal length. How to find the elements that are both in array1 and array2? Thanks!!!

[Glenton]

Sounds like a job for sets.
See docs here

In [21]: a
Out[21]: array([1, 2, 3, 4])

In [22]: b
Out[22]: array([2, 4, 4, 5, 5])

In [23]: a2=set(a)

In [24]: b2=set(b)

In [25]: a2
Out[25]: set([1, 2, 3, 4])

In [26]: b2
Out[26]: set([2, 4, 5])

In [27]: result = a2 & b2 #or a2.intersection(b2)

In [28]: result
Out[28]: set([2, 4])

Or you could loop through one of the arrays and check whether it's in the other.

In [29]: for i in a:
   ....:     if i in b:
   ....:         print i,
   ....:         
   ....:         
2 4