Python: Determine Missing Line

Question

Take for example a short file consisting of these lines:

Apple = 1
Pear = 1
Orange = 2
;
Orange = 3
Pear = 1
;
Apple = 1
Pear = 1
Orange = 1

What I did was to readline the text file, and put Apple, Orange and Pear into their respective lists such as:

Orange = [ 2,3,1 ]
Pear = [ 1,1,1 ]

I used line.count('Apple')==1 to identify that the current line in the text file is a fruit and then append the value after = to the list.

As you can see, the second section is missing Apple. I want the list to be:

Apple = [ 1,'-',1]

Whenever the line does not show a fruit, the list should append - to indicate it.

My question is, how then can I do it ie. to determine that a section is missing a fruit name and then to append - to it.

Answer 1

You could keep an array with all the fruit names found in a section. When you encounter a semicolon you check for each fruit if its name exists in the array and append a '-' if it does not, then you clear the array and continue with the next section.

Answer 2

if line.count('Apple')==1:
    Apple.append(str(number))
else:
    Apple.append('-')

Answer 3

from collections import defaultdict
from itertools import takewhile

d = defaultdict(list)
valid_fruits = set(['Apple', 'Pear', 'Orange'])

with open('data.txt') as f:
    while True:
        fruits = dict(takewhile(lambda x: x[0] != ';',
                                (line.rstrip().split(' = ') for line in f)))
        if not fruits:
            break
        for fruit in valid_fruits:
            if fruit in fruits:
                d[fruit].append(int(fruits[fruit]))
            else:
                d[fruit].append('-')

print d

Output:

defaultdict(<type 'list'>, {'Orange': [2, 3, 1], 'Pear': [1, 1, 1], 'Apple': [1, '-', 1]})