[:, i] what does this mean python code example

Example 1: python mean

# Probably the most convenient set of statistics functions are found
# in the Numpy package

# Basic syntax:
import numpy as np
np.mean(your_list) # Calculate mean
np.median()	# Calculate median
np.std()	# Calculate standard deviation
np.var()	# Calculate variance

Example 2: mean python

import numpy as np
values=[1,10,100]
print(np.mean(values))
values=[1,10,100,np.nan]
print(np.nanmean(values))