searching Python Dictionary

Question

I need to delete a entry from a list in Python. Here's what it contains:

{'Other': '1.05', 'United States': '93.67', 'Liberia': '3.26', '" alt="" />\n</p>\n</div>': '', 'Canada': '2.02'}

I know I can type:del List_Of_Countries['Canada'] That works perfectly but I am having trouble selecting the one that says " alt="" />\n</p>\n</div>

I think its because of the extra double quote, but I have a few lists that have similar entries so is there an easy way to simply search for the one that either contains "alt" or has " as a value of the key(so I can learn and apply it to other situations)?

possible duplicate of [Search of Dictionary Keys python](http://stackoverflow.com/questions/5174506/search-of-dictionary-keys-python) — Chinmay Kanchi, Mar 14 '11 at 20:54
May be you need a raw string: `List_Of_Countries[r'" alt="" />\n\n']` — Paulo Scardine, Mar 14 '11 at 20:56
no error or anything, just trying to figure out how to search by string as opposed to entering the entire string or how to search by values (i.e. all values that are blank or only contain a single double quote). It would be great if someone could point me out to a place to learn. — Lostsoul, Mar 14 '11 at 20:57

score 4 · Answer 1 · answered Mar 14 '11 at 20:56

>>> x = {'Other': '1.05', 'United States': '93.67', 'Liberia': '3.26', '" alt="" />\n</p>\n</div>': '', 'Canada': '2.02'}
>>> del x['Canada']
>>> x
{'United States': '93.67', 'Liberia': '3.26', 'Other': '1.05', '" alt="" />\n</p>\n</div>': ''}
>>> del x['" alt="" />\n</p>\n</div>']
>>> x
{'United States': '93.67', 'Liberia': '3.26', 'Other': '1.05'}

Dynamically selecting keys based on some expression is not possible as dictionaries are implemented as hash maps, so the key is hashed internally. As such it is not possible to find a key which consists of something, as the hash would produce something completely else.

The only thing you can do is (obviously) loop through all elements and find the correct ones.

Thank you so much, so just to clarify there's nothing like alt* or something? — Lostsoul, Mar 14 '11 at 21:01
@Lostsoul: No, as the `alt*` would be computed using the hash function but wouldn't look where the other key starting with `alt` are. The hash of X is usually *very* different from the hash of Y even if X and Y are nearly identical. — poke, Mar 14 '11 at 21:04

Uku Loskit · Accepted Answer · 2011-03-14T21:04:27.623

2

a = {'Other': '1.05', 'United States': '93.67', 'Liberia': '3.26', '" alt="" />\n</p>\n</div>': '', 'Canada': '2.02'}
b = {}

for k, v in a.iteritems():
    if v == ''  or "alt" in k:
        pass
    else:
        b[k] = v
print b

a non-elegant, but working solution :D

edited Mar 14 '11 at 21:04

answered Mar 14 '11 at 20:59

Uku Loskit

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score 0 · Answer 3 · answered May 12 '13 at 14:12

dpath can solve this.

http://github.com/akesterson/dpath-python

Just setup a filter function that inspects the contents of the strings matching a glob, and pass it to the delete function. So if the stuff you want to delete lives in a dictionary:

$ easy_install dpath
>>> def filter(x):
>>> ... return (str(x) == r'" alt="" />\n</p>\n</div>')
>>> ...
>>> dpath.util.delete(MY_DICT, '*', filter=filter)

.... and that would delete all the objects in the dictionary that matched the string defined in your filter function.

searching Python Dictionary

3 Answers3