Python Data Structures and Algorithms

Dictionaries for text analysis

A common use of dictionaries is to count the occurrences of like items in a sequence; a typical example is counting the occurrences of words in a body of text. The following code creates a dictionary where each word in the text is used as a key and the number of occurrences as its value. This uses a very common idiom of nested loops. Here we are using it to traverse the lines in a file in an outer loop and the keys of a dictionary on the inner loop:

def wordcount(fname):     try:         fhand=open(fname)     except:         print('File cannot be opened')         exit()     count= dict()     for line in fhand:         words = line.split()         for word in words:             if word not in count:                 count[word] = 1             else:                 count[word] += 1     return(count) 

This will ...