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

     2 

     3 In the previous tutorial we saw the `for' loop and lists. Here we shall look into

     4 calculating mean for the same pendulum experiment and then move on to calculate

     5 the mean, median and mode for a very large data set.

     6 

     7 

     8 In []: g_list = []

     9 In []: for line in open('pendulum.txt'):

    10   ....     point = line.split()

    11   ....     L = float(point[0])

    12   ....     t = float(point[1])

    13   ....     g = 4 * pi * pi * L / (t * t)

    14   ....     g_list.append(g)

    15 

    16 In []: total = 0

    17 In []: for g in g_list:

    18  ....:     total += g

    19  ....:

    20 

    21 In []: g_mean = total / len(g_list)

    22 In []: print 'Mean: ', g_mean

    23 

    24 In []: g_mean = sum(g_list) / len(g_list)

    25 In []: print 'Mean: ', g_mean

    26 

    27 In []: g_mean = mean(g_list)

    28 In []: print 'Mean: ', g_mean

    29 

    30 

    31 In []: d = {'png' : 'image file',

    32       'txt' : 'text file', 

    33       'py' : 'python code'

    34       'java': 'bad code', 

    35       'cpp': 'complex code'}

    36 

    37 In []: d['txt']

    38 Out[]: 'text file'

    39 

    40 In []: 'py' in d

    41 Out[]: True

    42 

    43 In []: 'jpg' in d

    44 Out[]: False

    45 

    46 In []: d.keys()

    47 Out[]: ['cpp', 'py', 'txt', 'java', 'png']

    48 

    49 In []: d.values()

    50 Out[]: ['complex code', 'python code',

    51         'text file', 'bad code', 

    52         'image file']