Cheatography

# NumPy Cheat Sheet Cheat Sheet by mdesai96

### NumPy array basics

 ``np.arr­ay(­[1,­2,3])`` Creates a 1D array with values 1, 2, 3. (shape 1x3) ``np.arr­ay(­[(1­,2,3), (4,5,6)])`` Creates 2D array of shape 2x3 with values 1,2,3,­4,5,6 ``np.arr­ay(­[[(­1,2,3), (4,5,6)], [(7,8,9), (10,11­,12)]])`` Creates a 3D array with shape 2x2x3 ``np.zer­os(3,4)`` Creates a 3x4 array of zeros ``np.arr­ang­e(1­,60,5)`` Creates a 1D array of values 1 through 60 at steps of 5 ``a.resh­ape­(2,3,4)`` Reshapes array ``a`` into an array of shape 2x3x4 ``a.shape`` To get the shape of the array ``a``

### Subsetting

 ``a[0]`` Gets the 0th element in 1D array ``a`` ``b[0,0]`` Gets the 0th element in 2D array ``b`` ``c[0,0,0]`` Gets the 0th element in 3D array ``c`` ``c[9,0,0]`` Gets the element which is the 0th element in the 0th row in the 9th depth

### Slicing arrays

 1D arrays ``a[:]`` Selects everything ``a[2:5]`` Selects the 2nd through the 4th rows (does not include the 5th row) 2D arrays ``b[:,:]`` Selects all rows and all columns ``b[:,0]`` Selects all rows, and the zeroth column ``b[0,:]`` Selects the zeroth row, and all columns in that row ``b[0:2,:]`` Selects the zeroth and first row, but NOT the second. It includes all the columns in that row ``b[0:2,0:2]`` Selects the zeroth and first row, and the zeroth and first column 3D arrays ``c[:,:,:]`` Selects all rows and columns on all depths ``c[0,:,:]`` Selects the everything in the first depth ``c[:,0,:]`` Selects the first row of each depth ``c[:,:,0]`` Selects the first column of each depth