Python - Convert String into Iterable Integer List

Question

I am developing a Twitch Python IRC Bot that has a currency system. The balances of users are stored in a list, which is loaded from and saved to a text file. However, because the text file's content is loading into one singular string that is then placed inside the list, I cannot iterate through each entry in the string to add points to it. For example, here is the iterable list I'm looking for: [10, 21, 42, 5]

But, when this is saved to a text file and then loaded into the list, it turns out like this: ['10, 21, 42, 5', '0' (with a 0 entry added on). As you can see, this would iterate through the list with only recognizing 2 sections, which is where the quotations surround. Is there a way I can convert the string fetched from the text file into a list of integers that I can iterate through? Thanks in advance!

How are you saving to the text file, and how are you loading it? — Ng Oon-Ee, Feb 29 '16 at 06:06
Consider something like a dict that gets serialized with `json` instead. The `dict` keys can be user identifiers and the values can be the balances. — Brian Cain, Feb 29 '16 at 06:09
You'll probably get better answers if your post code (in a minimal fashion). — Jared Goguen, Feb 29 '16 at 06:30

score 1 · Answer 1 · answered Feb 29 '16 at 06:14

When you save to the file, you'll want to do so cleanly-- make sure that you write in a consistent format.

When you read from the file, I suggest using literal_eval from the ast package. This will turn any strings contained in the file into Python types.

score 1 · Answer 2 · answered Feb 29 '16 at 06:38

Have you tried writing the list to a yaml file instead of a text file?

import yaml

myfile = path/to/my/file
mylist = [10, 21, 42, 5]

with open(myfile,'w') as handle:
    yaml.dump(mylist, handle, default_flow_style=False)

with open(myfile,'r') as handle:
    retrieved_list = yaml.load(handle)

print retrieved_list

score 1 · Accepted Answer · answered Feb 29 '16 at 09:44

DISCLAIMER:

All the other answers are very good suggestions on good practices for storing data and reading them in later, but since you specifically asked how to "convert the string fetched from the text file into a list of integers ...", I will gladly help to do exactly such thing.

However, while this answer may be suitable for the exact thing you requested to be done, it is by no means the best practice to achieve what you want (saving in lists of integers, which would be better off done with JSON or YAML).

SOLUTION

Okay, this seems fairly simple.

You have an original list [10, 21, 42, 5].

You save it to a text file, then read it as a list only to find there are two sections (and they're giving back strings + what is that extra 0?!):

['10, 21, 42, 5', '0']

Seems like you only need the first section, so:

>>> x = ['10, 21, 42, 5', '0']
>>> y = x[0]
>>> print(y)
'10, 21, 42, 5'
>>> print(type(y))
str

But wait, that returns a string! Easy, just split by the separator ", ":

>>> z = y.split(", ")
>>> print(z)
['10', '21', '42', '5']

Now it returns a list, but it's still a list of strings, so all we got to do is convert every element of the list into type int (integer). This is easy enough to do with a standard for loop, but we can make this a one-liner with the map function:

...
>>> print(z)
['10', '21', '42', '5']
>>> z = map(int, z)  # apply int() to every elem; equi. to [int('10'), int('21'), int('42'), int('5')]
>>> print(z)
[10, 21, 42, 5]
>>> print(map(type, z))  # print out type of every element in list
[int, int, int, int]

CONCLUSION

So, given the read-in list of bizarre strings x = ['10, 42, 21, 5', '0'], you can get your desired list of integers with:

z = map(int, x[0].split(", "))

Python - Convert String into Iterable Integer List

3 Answers3

DISCLAIMER:

SOLUTION

CONCLUSION