Which is the best way to make a dictionary of lists? For instance, if I have lists list1, list2 and want to make a dictionary my_dict like that:
my_dict = ['list1': list1, 'list2': list2] I've found this example but the best answer is written in 2009. Maybe there are some new more laconic ways to do this?
You need to use curly rather than square brackets, but otherwise this is probably as good as it gets:
list1 = ['a', 'b', 'c'] list2 = [1, 2, 3, 4] my_dict = {'list1': list1, 'list2': list2} For a dictionary of lists, consider a defaultdict.
A normal dictionary works fine, but it raises an error if a key is not found.
list1 = list("abcd") list2 = [1, 2, 3, 4] d = {"list1": list1, "list2": list2} d["list3"] # KeyError: 'list3' This may be disruptive in some applications and may require additional exception handling.
The defaultdict behaves like a normal dict while adding some protection against errors.
import collections as ct dd = ct.defaultdict(list) dd.update(d) dd # defaultdict(list, {'list1': ['a', 'b', 'c', 'd'], 'list2': [1, 2, 3, 4]}) Adding a missing key will call the default factory function, i.e. list. Here instead of a error, we get an empty container:
dd["list3"] # [] This entry was added with an empty list.
dd # defaultdict(list, # {'list1': ['a', 'b', 'c', 'd'], # 'list2': [1, 2, 3, 4], # 'list3': []}) Convert a defaultdict to a regular dict by setting the default factory to None
dd.default_factory = None dd # defaultdict(None, {'list1': ['a', 'b', 'c', 'd'], 'list2': [1, 2, 3, 4]}) or by using the dict() builtin:
dict(dd) # {'list1': ['a', 'b', 'c', 'd'], 'list2': [1, 2, 3, 4]} If you want to turn the variable name into a key, here is a similar question.
If you just want a dictionary of lists with a sequential key.
def turn_to_dict(*args): return {i: v for i, v in enumerate(args)} lst1 = [1, 2, 3, 4] lst2 = [3, 4, 6, 7] lst3 = [5, 8, 9] v = turn_to_dict(lst1, lst2, lst3) >>> print(v) {0: [1, 2, 3, 4], 1: [3, 4, 6, 7], 2: [5, 8, 9]} This should work:
my_dict = dict([('list1', list1), ('list2', list2)]) Or, alternatively:
my_dict = {'list1': list1, 'list2': list2} The result will be the same.
Use the curly brace syntax to define the dictionary, and give each entry in your dictionary a key that corresponds to each value:
list_a = [1,2,3,4,5] list_b = [6,7,8,9,10] my_dict = {'list1':list_a, 'list2':list_b} 