I'm trying to create multiple lists like the following:
l1 = []
l2 = []
..
ln = []
Is there any way to do that?
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12Why not use a dictionary instead, or use a nested list? Whenever you are thinking: I need to generate variable names, stop. You want a dictionary instead, with your 'variable names' keys in that dictionary. If the names are sequential (numbered starting at 0 or 1), use a list instead.Martijn Pieters– Martijn Pieters2014-06-02 17:08:14 +00:00Commented Jun 2, 2014 at 17:08
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It is always better to tell what do you really want to implement -- I mean the bigger picture. The solution may be different than you think.pepr– pepr2014-06-25 18:56:02 +00:00Commented Jun 25, 2014 at 18:56
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2Does this answer your question? How do I create variable variables?wjandrea– wjandrea2021-08-22 18:00:29 +00:00Commented Aug 22, 2021 at 18:00
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6 Answers
What you can do is use a dictionary:
>>> obj = {}
>>> for i in range(1, 21):
... obj['l'+str(i)] = []
...
>>> obj
{'l18': [], 'l19': [], 'l20': [], 'l14': [], 'l15': [], 'l16': [], 'l17': [], 'l10': [], 'l11': [], 'l12': [], 'l13': [], 'l6': [], 'l7': [], 'l4': [], 'l5': [], 'l2': [], 'l3': [], 'l1': [], 'l8': [], 'l9': []}
>>>
You can also create a list of lists using list comprehension:
>>> obj = [[] for i in range(20)]
>>> obj
[[], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], []]
>>>
2 Comments
BeetDemGuise
You could do
[[]]*20 instead of using the range function.lowzhao
[[]] * 20 gives you a list of 20 references for the inner [ ] instead, this is incorrect. Try appending 1 value into the list, all of them will have that values too. Indeed if L = [[]]*20 then L[0] is L[1] will be TrueYou can use dictionary comprehension:
obj = {i:[] for i in list(range(1,5))}
Comments
Just Extending Already Accepted Answer, Using Enumerate to initiate default values in list. Accessing list and adding values which was not mentioned.
range_list = list(range (int(input())))
obj = {}
for i, j in enumerate(range_list): # assigning default values
obj['l'+str(i)] = [j**2]
print(obj['l0'])
print(type(obj['l0']))
obj['l0'] = list(range(5)) # accessing list
print(obj['l0'])
#3 asking user, how many list to be created
#[0] default value in first list
#<class 'list'>
#[0, 1, 2, 3, 4] current value in first list
#[Program finished]
3 Comments
Rishabh Kumar
Could you provide more details about your answer. Please have a look at stackoverflow.com/help/how-to-answer
Subham
what part were you not able to understand? I am just extending already accepted answer and have made lots of comments.
Rishabh Kumar
Try adding a line towards how your answer is different. See other posts in this thread to get an idea of what I am talking about.
You can simply use a for loop to create n lists.
for i in range(10):
a_i = [i] #Stores the corresponding value of i in each a_i list.
print(a_i)
The variable a_i changes as i increments, so it becomes a_1, a_2, a_3 ... and so on.
Comments
there is a way to do that if you want to create variables. but instead, u should use a dictionary as mentioned above. but anyway I am going to show you how to create variables as you asked.
for i in range(num_vars):
globals()[f'ls{i}'] = []
print(ls1) # lsn should work
