import numpy as np 
import matplotlib.pyplot as plt array = np.array([[1,2,3,4,5,6],[10,20,30,40,50,60],[3,4,5,6,7,8],[100,200,300,400,500,600]])def plot(list):fig = plt.figure()ax = fig.add_subplot(111)for a,i in enumerate(list.T):ax.scatter(i[0],i[1],c='red') # This is plottedax.plot(i[2],i[3],'g--') # THIS IS NOT BEING PLOTTED !!!! fig.show()plot(array)

Now, I need to call plot several times using different array lists. So my for loop cannot be removed. Is there any other way to plot a dotted line apart from calling plt.plot instead ?

This is the plot I get:

As you can see, I am not getting the plt.plot(i[2],i[3],'g--'). Why is this so ?

But when you print the values using the same for loop:

In [21]: for a,i in enumerate(array.T):...:     print i[2],i[3]...:     
3 100
4 200
5 300
6 400
7 500
8 600

The values are perfectly printed. They however are not plotted.

Remove the for loop:

ax.scatter(array[0],array[1],c='red')
ax.plot(array[0],array[1],'g--')

The problem with your code is that you iterate over rows, which is fine for plotting single dots (ax.scatter), but not for connecting single dots (ax.plot with '--' option): at each row you only plot the line between that point and itself, which obviously doesn't show up in the graph.