Python convert string to list (No .split())

Question

I've got a little problem:

I have a String in my Database which is called actions. Now, I'm writing a method, which gets that string from the database (that works), and then I want to turn that string into a list.

I know actions.split(), but this didn't work out so well for me, because if my string looks like this:

actions = [
    {u'action': 'visit_testing', u'timestamp': datetime.datetime(2016, 2, 12, 13, 32, 14)},
    {u'action': 'visit_foo', u'timestamp': datetime.datetime(2016, 2, 12, 13, 37, 50)}
]

I can't use actions.split(', ') because it would mess up the dictionaries inside.

Till now I've got the following code:

timestamp = datetime.now().replace(microsecond=0)
dict = {'timestamp': timestamp, 'action': action}

if self.actions:
    actions_string = str(self.actions)
    actions_stripped = actions_string.strip('[')
    actions_stripped = actions_stripped.strip(']')
    actions_splitted = actions_stripped.split(', ')

    new_action_list = []

    buffer = ''
     for string in actions_splitted:
        if '{' in string:
            buffer = str(string)
        elif '}' in string:
            buffer = buffer + ', ' + str(string)
            new_action_list.append(str(buffer))
            buffer = ''
        else:
            buffer = buffer + ', ' + str(string)
    self.actions = str(buffer)
    self.last_action = datetime.now().replace(microsecond=0)
    self.save()
else:
    self.actions = '['+str(dict)+']'
    self.last_action = datetime.now().replace(microsecond=0)
    self.save()

Addition: If I run the method when actions is empty, it gives me a list with one dictionary, but if I run it when it already has something in it, if sets actions to "".

"I have a String in my Database", you have json forced in as a string in your database, it probably needs to be a JSONFieldor an actual object model — Sayse
– Sayse, Commented Feb 12, 2016 at 12:47

PM 2Ring · Accepted Answer · 2016-02-12 13:02:49Z

2

You should be using the json module to store valid JSON in your database. You can create a valid action list from that string using exec. But please beware that using exec or eval is a potentially dangerous practice.

import datetime

stuff = '''
actions = [{u'action': 'visit_testing', u'timestamp': datetime.datetime(2016, 2, 12, 13, 32, 14)}, {u'action': 'visit_foo', u'timestamp': datetime.datetime(2016, 2, 12, 13, 37, 50)}]
'''

exec(stuff)
print(actions)
print(actions[0]['timestamp'])

output

[{u'action': 'visit_testing', u'timestamp': datetime.datetime(2016, 2, 12, 13, 32, 14)}, {u'action': 'visit_foo', u'timestamp': datetime.datetime(2016, 2, 12, 13, 37, 50)}]
2016-02-12 13:32:14

answered Feb 12, 2016 at 13:02

PM 2Ring

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Comments

Benjamin · Accepted Answer · 2016-02-12 12:40:12Z

1

Use json library.

import json
my_dict_or_list = json.loads(your_string)

then work with Python objects. You will gain so much time :-D

answered Feb 12, 2016 at 12:40

Benjamin

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9 Comments

Red_C0der Over a year ago

now i'm getting Expecting property name enclosed in double quotes: line 1 column 3 (char 2)

Benjamin Over a year ago

json keys in dict are enclosed with double quotes, not simple quote. Can you have your string with these quotes ?

Red_C0der Over a year ago

I tried to change this line dict = {"timestamp": timestamp, "action": action}, but the quotes were changed back into single quotes... can i do .replace("'", '"')?

Benjamin Over a year ago

It should works but beware of string with escaped quote is your dict (i don't know if you can have some)

Håken Lid Over a year ago

Why use json.loads() on something that's not json?

|

Red_C0der · Accepted Answer · 2016-02-12 13:22:17Z

-2

I found a way that works for me:

    timestamp = datetime.datetime.now().replace(microsecond=0)

    if self.actions:
        new_dict = {"timestamp": timestamp, "action": action}
        #tmp_actions = json.loads(self.actions)
        tmp_actions = self.actions
        exec(tmp_actions)
        actions.append(new_dict)
        self.actions = str('actions = '+str(actions))
        self.last_action = datetime.datetime.now().replace(microsecond=0)
        self.save()
    else:
        exec('''actions = ['''+str({"timestamp": timestamp, "action": action})+''']''')
        self.actions = 'actions = '+str(actions)
        self.last_action = datetime.datetime.now().replace(microsecond=0)
        self.save()

Thanks for all the help.

answered Feb 12, 2016 at 13:22

Red_C0der

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4 Comments

bruno desthuilliers Over a year ago

This code will get you into trouble one day or another. Image what will happens if someone stores something like "os.system("rm -rf")" in your database...

Red_C0der Over a year ago

@brunodesthuilliers Yea, i know, but I guess I could write a method which checks if the text is "valid" (looks if a specific format is there)

bruno desthuilliers Over a year ago

As far as I'm concerned, I wouldn't bet my system security on this. Seriously, you'd better switch to (at least) json and write a run-once migration script for your current dat. Or use a properly normalized relational schema storing "actions" in their own table, one row per action.

Red_C0der Over a year ago

Well, I guess I'm going to create its own table then

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