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I'm doing a lot of lists and dictionary sorting...and this is causing memory errors in Python website.

Answer 1

+7 A:

If you only want the values you could just do:

mylist = stats.values()

If you need the key - value pair you should iterate the dict's items:

mylist = []
for k,v in stats.iteritems():
    mylist.append(v)

In the code in your question you are just iterating over the dicts keys.

Since you assign a single string (the key) to the tuple (k,v) it's characters are instead iterated; it's logical that this complete string cannot be unpacked' into a (k,v) tuple unless in a situation where you would have a string with a length of exactly two. That explains the error message: you're trying to unpack every single character of the string into only two placeholders (k and v).

ChristopheD 2010-04-02 23:19:09

just nitpicking, but as @Dave Kirby points out they keys are actually being unpacked, as strings character by character and hence too _many_ values to unpack

Davy8 2010-04-02 23:48:09

If you actually do want to iterate over both the keys and values, I would suggest using `stats.iteritems()` instead of `stats.items()` because it doesn't create a whole new list of the dictionary's contents.

David Zaslavsky 2010-04-02 23:51:36

@Davy8: yeah, updated my answer a little to make it a bit more clear...

ChristopheD 2010-04-02 23:53:41

@David: yes, that would be a good fit for this situation.

ChristopheD 2010-04-02 23:59:49

Answer 2

+5 A:

The problem is that when you iterate through a dictionary using a for ... in ... loop you only iterate through the keys. You can demonstrate this with:

>>> for x in stats: print x
... 
2010-03-19
2010-03-18
etc

so when you do for k,v in stats: it is trying to assign a string to the tuple (k,v). Since strings are iterable it will try to assign a character at a time, so it would assign '2' to k and '0' to v, but has nowhere to assign the remaining characters to - hence the error.

What you want is to either call the dict iteritems method to get a sequence of (key, value) tuples, or to call the itervalues method to get a sequence of the values since you are not using the key.

Dave Kirby 2010-04-02 23:34:27

Answer 3

+1 A:

The default behavior when iterating a dictionary is equivalent to calling its keys() method.

So the following are equivalent:

>>> for k in stats: print k
>>> for k in stats.keys(): print k

If you want to iterate over keys and values in a single run, you must call items().

jathanism 2010-04-02 23:40:29

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I'm doing a lot of lists and dictionary sorting...and this is causing memory errors in Python website.

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