How to find the name of a list in a list of lists instead of its value?

user_10813239 0
Viewed 15870

I am trying to find the name of a list in a list of lists (is there a specific name for "list of lists"?).

For example I have the following lists:

x= ["a","b"]
y= ["c","d"]
z= [x,y]

If I now want to know what is the name of the first list in list "z" I would try like that:

print(z[0])

But instead of "x" I get the value of x ("a","b")

  • How can I get the output "x"?
python-3.x list python
5 Answers

You want to use a dictionary instead of a list. Where a list is just an enumeration of values, a dictionary is a key-value data structure.

This is how your example would look as a dictionary literal:

{
    "x": ["a", "b"],
    "y": ["c", "d"],
}

Unlike a list, a dictionary does not preserve the order of elements however! If you had an application where you needed to preserve order, you can use an OrderedDict. UPDATE: This paragraph is no longer true as of Python 3.7.

user_33685720

Having the name of variable as your output is not possible, unless you change some strategies in your code, for e.g:

x = ["a", "b"]
y = ["c", "d"]
z = {'x': x, 'y': y}

using dictionaries might be better suited to your problem. You can then search for value ["a", "b"] and reach the name 'x'.

user_89574160

Maybe just put the list name at the start of each list and instead use z[0][0] to get the name?

user_78518970

a list is a mutable datatype in python. so with

x = ["a", "b"]

python will allocate some memory and store the adress in x. so x is internally something like:

<List with data at 0x123456789>

when you make z, python allocates some memory and stores the adress in z then, it will store the adresses of x and y in the memory of z. so z is internally:

[<List with data at 0x123456789>, <List with data at 0x987654321>]

now you can see that there is no information of the name of the variable which also stores the adress 0x123456789

Summary: you can't get the variable name of a list object.

user_87330660

Python3

#!/usr/bin/env python
#getGlobalNames.py
# Example Globals
someVar='foo';empty=[];someLst=['thing1','thing2']
def jam(treble=True,bass=11):someJam=(treble,base)
# Names you are looking for...
obs=[empty,someLst,jam]
# doStuff
globs=list(globals().items())# globals to static
oX=[]
for o in obs:
    for glob in globs:
        if glob[1]==o:oX.append(glob)
for o in oX:print('Name:',o[0],'\nStuff:\n',o[1])

Out:

RESTART: ./getGlobalNames.py
Name: empty 
Stuff:
 []
Name: someLst 
Stuff:
 ['thing1', 'thing2']
Name: jam 
Stuff:
 <function jam at 0x7f89f8e775e0>
>>>
user_192779630
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