Question

New to Python, and have a very basic question:

I have a text file, which is formatted like the following example (the first number is a date, the second a value assosiated with it):

4.12. -11
5.12. 24
6.12. 192
7.12. -34
8.12. 921

I need a way to find the ‘value’ from the text file, for further use. The values can be pretty much anything – as long as they are numbers.

Answer 1

If you have only one vale separated by number of spaces (whitespace characters, to be precise):

data = {}

with open('filename') as f:
    for line in f:
        row = line.split()
        data[row[0]] = row[1]

Assumptions: the keys in first column are unique.

now you can access data[value] to get the value, for example:

>>> print data['8.12.']
921

If you can have multiple values per key/date, then:

from collections import defaultdict

data = defaultdict(list)

with open('filename') as f:
    for line in f:
        row = line.split()
        data[row[0]].append(row[1])

Now the data will be a dictionary and values will be list of all values found in file. Therefore for file:

1.1. 10
2.1. 11
1.1. 12

The data['1.1'] will be ["10", "12"]

You might have to add conversion of string to number to fully fit your requirements:

data[row[0]] = int(row[1])

or:

data[row[0]] = float(row[1])