nested-lists

This question already has an answer here: Convert string representation of list to list 16 answers Say I have a string representing some nested lists and I want to convert it into the real thing. I could do this, I think: exec "myList = ['foo', ['cat', ['ant', 'bee'], 'dog'], 'bar', 'baz']" But in an environment where users might be supplying the string to execute this could/would be a bad idea. Does anybody have any ideas for a tidy parser that would accomplish the same thing? >>> import ast >>> mylist = ast.literal_eval("['foo', ['cat', ['ant', 'bee'], 'dog'], 'bar', 'baz']") >>> mylist [

I am trying to copy the nested list a , but do not know how to do it without using the copy.deepcopy function. a = [[1, 2], [3, 4]] I used: b = a[:] and b = a[:][:] But they all turn out to be shallow copy. Any hints? My entry to simulate copy.deepcopy : def deepcopy(obj): if isinstance(obj, dict): return {deepcopy(key): deepcopy(value) for key, value in obj.items()} if hasattr(obj, '__iter__'): return type(obj)(deepcopy(item) for item in obj) return obj The strategy: iterate across each element of the passed-in object, recursively descending into elements that are also iterable and making new

This question already has an answer here: List of lists changes reflected across sublists unexpectedly 13 answers I want to have a variable that is a nested list of a number of empty lists that I can fill in later. Something that looks like: my_variable=[[], [], [], []] However, I do not know beforehand how many lists I will need, only at the creation step, therefore I need a variable a to determine it. I thought about simple my_variable=[[]]*a , but that creates copies of lists and it is not what I want to have. I could do: my_variable=[] for x in range(a): my_variable.append([]) but I'm

I am trying to convert a nested list of lists into a list of tuples in Python 3.3. However, it seems that I don't have the logic to do that. The input looks as below: >>> nested_lst = [['tom', 'cat'], ['jerry', 'mouse'], ['spark', 'dog']] And the desired ouptput should look as exactly as follows: nested_lst_of_tuples = [('tom', 'cat'), ('jerry', 'mouse'), ('spark', 'dog')] Just use a list comprehension: nested_lst_of_tuples = [tuple(l) for l in nested_lst] Demo: >>> nested_lst = [['tom', 'cat'], ['jerry', 'mouse'], ['spark', 'dog']] >>> [tuple(l) for l in nested_lst] [('tom', 'cat'), ('jerry',

Lets say, there is a nested list, like: my_list = [[1, 2, 21], [1, 3], [1, 2]] When the function min() is called on this: min(my_list) The output received is [1, 2] Why and How does it work? What are some use cases of it? Bhargav Rao How are lists and other sequences compared in Python? Lists (and other sequences) in Python are compared lexicographically and not based on any other parameter. Sequence objects may be compared to other objects with the same sequence type. The comparison uses lexicographical ordering: first the first two items are compared, and if they differ this determines the

Using JSF 2.0, I need to display a table wherein each row contains a link which opens a popup. I have two models: A which has id and List<B> properties and B which has id and name properties. In my backing bean, I have a List<A> property. In my view, I am using <ui:repeat> to iterate over List<A> . The requirement is, depending on the row that the user clicks, the corresponding List<B> of A needs to be displayed. However, the <ui:repeat> does not accept a nested list to be assigned in the var attribute. Hence, I need to do a lot of workarounds which is not efficient. How do I efficiently solve

I've been tinkering in python this week and I got stuck on something. If I had a 2D list like this: myList = [[1,2],[3,4],[5,6]] and I did this >>>myList.index([3,4]) it would return 1 However, I want the index of something in side one of the lists, like this >>>myList.index(3) and it would return 1, 0 Is there anything that can do this? Cheers Try this: def index_2d(myList, v): for i, x in enumerate(myList): if v in x: return (i, x.index(v)) Usage: >>> index_2d(myList, 3) (1, 0) If you are doing many lookups you could create a mapping. >>> myList = [[1,2],[3,4],[5,6]] >>> d = dict( (j,(x, y))