1.Creating numpy array
import numpy as np# Create array of rank 1
tmp = np.array([1, 2, 3])# Create array of rank 2
tmp = np.array([[1, 2, 3], [4, 5, 6]])# Create array from tuple
tmp = np.array((1, 2, 3))# Create array of 0 of size 3 x 3
tmp = np.zeros((3, 3))# Create array of constant value (or text)
tmp = np.full((3, 3), 4) >> array([[4, 4, 4],
[4, 4, 4],
[4, 4, 4]])# Create array of random values (between 0 - 1)
tmp = np.random.random((3,3))# Create an array of sequence
tmp = np.arange(1,10,2) # range and step
tmp = np.arange(10) # starts from 0 and step not specified
tmp = np.linspace(0, 10, 5) # range and number of values
2.Accessing array using index
tmp = np.array([[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12],
[13, 14, 15, 16]])# Select first 2 rows and alternate columns 0 & 2
tmp1 = tmp[:2, ::2]# Select specific elements
tmp2 = tmp[[1, 1, 3],
[0, 2, 1]]>> array([5, 7, 14])# Selecting via conditions
tmp[tmp > 10]>> array([11, 12, 13, 14, 15, 16])
3.Basic operations
# Adding and subtracting to an array
tmp - 1# Sum all array elements
tmp.sum() #or
np.sum(tmp)>> 136# Square each element
tmp**2# Square root each element
np.sqrt(tmp)# Adding arrays (need to have the same # col)
tmp3 = tmp[[1, 1, 0, 3],
[0, 2, 1, 3]]>> array([ 5, 7, 2, 16])# tmp3 is added to every rowtmp + tmp3>> array([[ 6, 9, 5, 20],
[10, 13, 9, 24],
[14, 17, 13, 28],
[18, 21, 17, 32]])# Transpose
tmp = np.array([[1, 2, 3],
[4, 5, 6]])
tmp.T>> array([[1, 4],
[2, 5],
[3, 6]])# Min/Max
tmp.max()# Row wise Min/Max
tmp.max(axis=1)# Column wise Min/Max
tmp.max(axis=0)
4.Datatype
# Check datatype
tmp.dtype# Assign datatype
tmp = np.array([1, 2, 3], dtype=np.float64)
5.Split strings
# Split string (default split on space)
tmp = np.array('Breakfast at Tiffanys')
np.char.split(tmp)# Split string using delimiter
tmp = np.array(‘Breakfast-at-Tiffanys')
np.char.split(tmp, sep=‘-')
