What I have is a list where the elements are an array like this:
([1,2,3],[4,5,6],[7,8,9])
What I want is to find the index of an element in this list, something like:
list.index([4,5,6]) #should return 1.
Problem is numpy array comparison throws up errors unless you put something like: (A==B).all()
But this comparison is inside the index function so i can't and don't really want to add the all() bit to the function. Is there an easier solution to this?
Your last error message indicates that you are still mixing lists and arrays. I'll try to recreate the situation:
Make a list of lists. Finding a sublist works just fine:
In [256]: ll=[[1,2,3],[4,5,6],[7,8,9]]
In [257]: ll.index([4,5,6])
Out[257]: 1
Make an array from it - it's 2d.
In [258]: la=np.array(ll)
In [259]: la
Out[259]:
array([[1, 2, 3],
[4, 5, 6],
[7, 8, 9]])
It does not have an index method
In [260]: la.index([4,5,6])
...
AttributeError: 'numpy.ndarray' object has no attribute 'index'
Make it a list - but we get your ValueError:
In [265]: list(la).index([4,5,6])
...
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
That's because list(la) returns a list of arrays, and arrays produce multiple values in == expressions:
In [266]: list(la)
Out[266]: [array([1, 2, 3]), array([4, 5, 6]), array([7, 8, 9])]
The correct way to produce a list from an array is tolist, which returns the original ll list of lists:
In [267]: la.tolist().index([4,5,6])
Out[267]: 1
If you are starting with a numpy array, you can get the result that you want by converting it to a list of lists before using the index() function, e.g.:
import numpy as np
arr = np.array([[1,2,3],[4,5,6],[7,8,9]])
lst = [list(x) for x in arr]
print (lst.index([4,5,6]))
... which gives the expected output 1.
arr.tolist() == lst
numpyarrays? They are not the same thing. Don't mix-n-match. And this thing that you are looking for - will it always be a sublist or row (of an array)?a==bis an numpy array, so the result is also an array. But that expression occurs where Python expects a scalar boolean. Test your code in small pieces.==test.