Parsing Input File in Python

Question

I have a plain text file with some data in it, that I'm trying to open and read using a Python (ver 3.2) program, and trying to load that data into a data structure within the program.

Here's what my text file looks like (file is called "data.txt")

NAME: Joe Smith
CLASS: Fighter
STR: 14
DEX: 7

Here's what my program looks like:

player_name = None
player_class = None
player_STR = None
player_DEX = None
f = open("data.txt")
data = f.readlines()
for d in data:
    # parse input, assign values to variables
    print(d)
f.close()

My question is, how do I assign the values to the variables (something like setting player_STR = 14 within the program)?

akaRem · Accepted Answer · 2012-12-15 17:22:10Z

2

player = {}
f = open("data.txt")
data = f.readlines()
for line in data:
    # parse input, assign values to variables
    key, value = line.split(":")
    player[key.strip()] = value.strip()
f.close()

now the name of your player will be player['name'], and the same goes for all other properties in your file.

edited Dec 15, 2012 at 17:22

akaRem

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answered Dec 15, 2012 at 16:11

bigblind

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Comments

lucemia · Accepted Answer · 2012-12-15 16:12:44Z

1

import re

pattern = re.compile(r'([\w]+): ([\w\s]+)')

f = open("data.txt")
v = dict(pattern.findall(f.read()))
player_name = v.get("name")
plater_class = v.get('class')
# ...


f.close()

answered Dec 15, 2012 at 16:12

lucemia

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2 Comments

bigblind Over a year ago

Why go through the hussle of searching the entire file with a regex, if you know the format of the file will be a key:value pair on every line?

akaRem Over a year ago

Did you run this code? It founds nothing. Because "NAME: Joe Smith" != "name: Joe Smith"

Raymond Hettinger · Accepted Answer · 2012-12-15 16:37:14Z

0

The most direct way to do it is to assign the variables one at a time:

f = open("data.txt")              
for line in f:                       # loop over the file directly
    line = line.rstrip()             # remove the trailing newline
    if line.startswith('NAME: '):
        player_name = line[6:]
    elif line.startswith('CLASS: '):
        player_class = line[7:]
    elif line.startswith('STR: '):
        player_strength = int(line[5:])
    elif line.startswith('DEX: '):
        player_dexterity = int(line[5:])
    else:
        raise ValueError('Unknown attribute: %r' % line)
f.close()

That said, most Python programmers would stored the values in a dictionary rather than in variables. The fields can be stripped (removing the line endings) and split with: characteristic, value = data.rstrip().split(':'). If the value should be a number instead of a string, convert it with float() or int().

edited Dec 15, 2012 at 16:37

answered Dec 15, 2012 at 16:13

Raymond Hettinger

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3 Comments

Bartlomiej Lewandowski Over a year ago

how about for the sake of performance, assign the fields to the variables already? Something like strip the name, and assign the number/string to the field in object named same as the stripped string. Would that work?

Raymond Hettinger Over a year ago

Performance is a red-herring here. The OP's task is IO bound, so the time to read the file dominates the processsing. Also, direct variable assignment uses a dictionary (globals) behind the scences, so there isn't any essential difference between the two approaches.

akaRem Over a year ago

What if DEX:14 or dex: 14? It would be unknow attr, but is it really unknown?

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