CODEWITHSUNDEEP
pythonnumpyindexingnested
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Reputation: 3438

Store Slice Index as Object

Say I have a list of lists of lists etc... of some depth:

ExampleNestedObject = numpy.ones(shape = (3,3,3,3,3))

In general I can get an element by writing:

#Let:
#a, b, c, d, e -> are integers

print ExampleNestedObject[a][b][c][d][e]

#numpy also happens to allow:

print ExampleNestedObject[(a,b,c,d,e)]

#python in general allows:

print ExampleNestedObject[a,b,:,d,e]

My question is -> how can I store the index "a,b,:,d,e" as an object?

SomeSliceChoice = a,b,:,d,e

print ExampleNestedObject[SomeSliceChoice]

Upvotes: 4

Views: 1966

Answers (1)

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Reputation: 3438

The trick is to think of an index object as a tuple of slice objects.

Example1:

Object[1,2,:] == Object[(1,2,slice(None,None,None))]

Example2:

WantedSliceObject = (1,2,slice(None,None,None), 4,5)
Object[1,2,:,4,5] == Object[WantedSliceObject]

Note the syntax of '''slice:

#slice(start, stop[, step])

#1 ==  slice(1, 2, 1)

WantedSliceObject2 = (
   slice(1, 2, 1),
   slice(2, 2, 1),
   slice(None,None,None), 
   slice(4, 2, 1),
   slice(5, 2, 1)
   )

#WantedSliceObject2 == WantedSliceObject

Upvotes: 8

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