PythonQ 240-8XX Manuale Utente Scaricare il pdf (Pagina 16)

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More advanced array indexing

>>> a = linspace(0, 29, 30)

>>> a.shape = (5,6)

>>> a

array([[ 0., 1., 2., 3., 4., 5.,]

[6.,7.,8.,9.,10.,11.,]

[12.,13.,14.,15.,16.,17.,]

[18.,19.,20.,21.,22.,23.,]

[24.,25.,26.,27.,28.,29.,]])

>>> a[1:3,::2] # a[i,j] for i=1,2 and j=0,2,4

array([[ 6., 8., 10.],

[12., 14., 16.]])

>>> a[::3,2::2] # a[i,j] for i=0,3 and j=2,4

array([[ 2., 4.],

[20., 22.]])

>>> i = slice(None, None, 3); j = slice(2, None, 2)

>>> a[i,j]

array([[ 2., 4.],

[20., 22.]])

Numerical Python – p. 250/728

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PythonQ 240-8XX Manuale Utente Pagina 16