python: unpacking a string to a list

问题:

The answer to a question on multiple-value elements in a config file (which exactly fits my needs) suggests to "unpack the string from the config". I read the doc for unpacking arguments lists suggested in several places but I fail to understand how this relates to my problem.

I am sure this must be obvious: having a string str = "123,456", how can I transform it into the list [123,456] (the number of elements separated by a comma in the string may vary)

Thank you.

回答1:

Do you want a list of strings or a list of ints?

If you just want a list of strings, it's very simple:

my_list = my_string.split(',')

If you want to convert these to ints, you need:

my_list = map(int, my_string.split(','))

(Also, don't use str as a variable name as it shadows the built-in str() function.)

回答2:

[int(x) for x in str.split(",")]

You're basically applying the function int to each element produced by split of your string.

The result of simply str.split(',') would be ["123","456"].

As Daniel Roseman pointed out, you should be careful not to use variable or method names that inadvertently overshadow built in methods, like, for instance, str.

回答3:

The easiest way would be to use split().

unpacked = str.split(',')

回答4:

Although I agree with the other answers, you should also handle exceptions in the case of invalid string representation of a supposed number. Take, for example, the following snippet:

number_string = "123,456,x21"
delimiter = ","
number_list = []
for item in number_string.split(delimiter):
    try:
        my_num = int(item)
        number_list.append(item)
    except ValueError, e:
        # you can choose to just pass or handle the error like so
        print "Skipping %s: %s" % (item, e.message)

Just a thought. Good luck!