defaultdict

问题 I want to create a default dictionary in which the default values are negative infinity. I tried doing defaultdict(float("-inf")) but it is not working. How do I do this? 回答1: As the traceback specifically tells you : >>> from collections import defaultdict >>> dct = defaultdict(float('-inf')) Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> dct = defaultdict(float('-inf')) TypeError: first argument must be callable and per the documentation (emphasis mine): If

问题 I need to parse a file which has contents that look like this: 20 31022550 G 1396 =:0:0.00:0.00:0.00:0:0:0.00:0.00:0.00:0:0.00:0.00:0.00 A:2:60.00:33.00:37.00:2:0:0.02:0.02:40.00:2:0.98:126.00:0.98 C:0:0.00:0.00:0.00:0:0:0.00:0.00:0.00:0:0.00:0.00:0.00 G:1391:60.00:36.08:36.97:719:672:0.51:0.01:7.59:719:0.49:126.00:0.50 T:1:60.00:33.00:37.00:0:1:0.37:0.02:47.00:0:0.00:126.00:0.18 N:0:0.00:0.00:0.00:0:0:0.00:0.00:0.00:0:0.00:0.00:0.00 +A:2:60.00:0.00:37.00:2:0:0.67:0.01:0.00:2:0.65:126.00:0.65

问题 So the defaultdict documentation mentions that, if an item is missing, the value returned by default_factory "is inserted in the dictionary for the key, and returned." That's great most of the time, but what I actually want in this case is for the value to be returned but not inserted into the defaultdict. I figured I could probably subclass defaultdict and override... I guess __missing__ ? Not sure. What's the best way to go about this? Thanks in advance. 回答1: You can subclass dict and

问题 I posted a similar question about an hour ago, but have since deleted it after realising I was asking the wrong question. I have the following pickled defaultdict : ccollections defaultdict p0 (c__builtin__ list p1 tp2 Rp3 V"I love that" p4 (lp5 S'05-Aug-13 10:17' p6 aS'05-Aug-13 10:17' When using Hadoop, the input is always read in using: for line in sys.stdin: I tried reading the pickled defaultdict using this: myDict = pickle.load(sys.stdin) for text, date in myDict.iteritems(): But to no

问题 Given three dicts d1, d2 and d3: d1 {'a':1,'b':2,'c':3, 'd':0) d2 {'b':76} d3 {'a': 45, 'c':0} There are some key names that are common to more than one dict (and in reality, they will represent the same real-life object). Others such as 'd' in d1 only exist in d2. I want to group all dicts together, first summing the values of the common keys first, ending up with: {'a':46, 'b':78, 'c':3, 'd': 0} If every dict were the same size and contained the same keys, I could do something like:

问题 I have a list of dictionaries. Let's call it: list_of_dict . The dictionaries in the list are in the form: {'a' : 1, 'b' : 5, 'c' : 3, 'd' : 6} and {'a' : 3, 'f' : 2, 'g' : 1, 'h' : 3, 'i' : 5, 'j' : 3} I have another list called list_to_match which only holds some letters: ['a', 'f', 'x'] I need to iterate over list_of_dict and find the keys that match with the element in the list and append the values to a an empty defaultdict of list items. If not found, append 0 to the list. The

问题 When using min() on a defaultdict object, it strangely returns the maximum if used on a dict counting indices of a string. For example: >>> import collections >>> defaultdict=collections.defaultdict >>> x=defaultdict(int) >>> string="lol I am a lol noob" >>> for k in string: x[k]+=1 >>> x defaultdict(<type 'int'>, {'a': 2, ' ': 5, 'b': 1, 'I': 1, 'm': 1, 'l': 4, 'o': 4, 'n': 1}) >>> min(x.items()) (' ', 5) 回答1: items() returns the items as (key, value) tuples. This means that when they are

问题 In the following code: from collections import defaultdict confusion_proba_dict = defaultdict(float) for i in xrange(10): confusion_proba_dict[i] = i + 10 print confusion_proba_dict Output is: defaultdict(<type 'float'>, {0: 10, 1: 11, 2: 12, 3: 13, 4: 14, 5: 15, 6: 16, 7: 17, 8: 18, 9: 19}) But, I need output to be: {0: 10, 1: 11, 2: 12, 3: 13, 4: 14, 5: 15, 6: 16, 7: 17, 8: 18, 9: 19} How can I do it? 回答1: just transform it to a regular dict print( dict(confusion_proba_dict) ) but if you

问题 This question already has answers here : creating a defaultlist in python (2 answers) Closed 3 years ago . Is there\How would you build an equivalent of python's very useful collections.defaultdict? Imagined usage of such a container: >>> a = collections.defaultlist(0) >>> a[2]=7 >>> a[4]='x' >>> a [0,0,7,0,'x'] UPDATE: I've added a follow up question to add even more functionality to this construct 回答1: I think this would be a bit confusing to use; however, here's my first thought on how to

问题 I have a nested dictionary that contains bookmarks that were read from csv. Each level of nesting can have sub-folders and bookmarks. I need to make sure that I properly indent the sub-folders and bookmarks when I print them out. With my current code, all sub-folders are indented at the same level. This makes it appear as if my parent folder only has one level of nesting, but this is not the case. My bookmarks should have My code is: with open('urls.csv') as bookmarks_input: reader = csv