Hello welcome to the tutorial on statistics and dictionaries in Python.

In the previous tutorial we saw the `for' loop and lists. Here we shall look into
calculating mean for the same pendulum experiment and then move on to calculate
the mean, median and mode for a very large data set.


In []: g_list = []
In []: for line in open('pendulum.txt'):
  ....     point = line.split()
  ....     L = float(point[0])
  ....     t = float(point[1])
  ....     g = 4 * pi * pi * L / (t * t)
  ....     g_list.append(g)

In []: total = 0
In []: for g in g_list:
 ....:     total += g
 ....:

In []: g_mean = total / len(g_list)
In []: print 'Mean: ', g_mean

In []: g_mean = sum(g_list) / len(g_list)
In []: print 'Mean: ', g_mean

In []: g_mean = mean(g_list)
In []: print 'Mean: ', g_mean


In []: d = {'png' : 'image file',
      'txt' : 'text file', 
      'py' : 'python code'
      'java': 'bad code', 
      'cpp': 'complex code'}

In []: d['txt']
Out[]: 'text file'

In []: 'py' in d
Out[]: True

In []: 'jpg' in d
Out[]: False

In []: d.keys()
Out[]: ['cpp', 'py', 'txt', 'java', 'png']

In []: d.values()
Out[]: ['complex code', 'python code',
        'text file', 'bad code', 
        'image file']