how to plot bar chart for a list in python

Change this line:

import numpy

to:

import numpy as np

Change this line:

labels, values = zip(*top[])

to:

labels, values = zip(*top)

With those errors out of the way:

Using axes methods:

import numpy as np                                                               
import matplotlib.pyplot as plt  

top=[('a',1.875),('c',1.125),('d',0.5)]

labels, ys = zip(*top)
xs = np.arange(len(labels)) 
width = 1

fig = plt.figure()                                                               
ax = fig.gca()  #get current axes
ax.bar(xs, ys, width, align='center')

#Remove the default x-axis tick numbers and  
#use tick numbers of your own choosing:
ax.set_xticks(xs)
#Replace the tick numbers with strings:
ax.set_xticklabels(labels)
#Remove the default y-axis tick numbers and  
#use tick numbers of your own choosing:
ax.set_yticks(ys)

plt.savefig('netscore.png')

Using plt methods:

import numpy as np                                                               
import matplotlib.pyplot as plt

top=[('a',1.875),('c',1.125),('d',0.5)]

labels, ys = zip(*top)
xs = np.arange(len(labels)) 
width = 1

plt.bar(xs, ys, width, align='center')

plt.xticks(xs, labels) #Replace default x-ticks with xs, then replace xs with labels
plt.yticks(ys)

plt.savefig('netscore.png')

you are calling numpy but you are not using it

on the line

indexes = np.arange(len(labels))

i guess you were trying to use it, either do:

import numpy as np

or:

indexes = numpy.arange(len(labels))