Find if value exists in multiple lists

Question

I have 4 list and each element on the list are unique across the 4 list. How do I find if the value exist in one of the list and return which list it exist?

Example

Answer 1

Given your updated question, let's assume the a, b, c, d variables are in the global scope

value = 'a'
a = ['a','b','c']
b = ['d','e','f']
d = ['g','h','i']
c = ['j','k','l']

w = next(n for n,v in filter(lambda t: isinstance(t[1],list), globals().items()) if value in v)
print(w)

produces

a

i.e. the name of the first list in the global namespace that contains value

If the variables are in a local scope, e.g. within a function, you can use locals() instead

def f():
    a = ['a','b','c']
    b = ['d','e','f']
    d = ['g','h','i']
    c = ['j','k','l']
    w = next(n for n,v in filter(lambda t: isinstance(t[1],list), locals().items()) if value in v)
    print(w)

f()

produces

a

Note: you might want to adopt a naming convention to target a specific group of variables, e.g. targ_ as a prefix

targ_a = ['a','b','c']
targ_b = ['d','e','f']
targ_d = ['g','h','i']
targ_c = ['j','k','l']
w = next(n for n,v in filter(lambda t: isinstance(t[1],list) and t[0].startswith('targ_'), globals().items()) if value in v)
print(w)

produces

targ_a

To explain things a bit more in detail, let's have a look at what the globals() call returns. For example using the python shell

Python 3.4.3 (default, Oct 14 2015, 20:28:29) 
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> value = 'a'
>>> targ_a = ['a','b','c']
>>> targ_b = ['d','e','f']
>>> targ_d = ['g','h','i']
>>> targ_c = ['j','k','l']
>>> globals()
{'targ_d': ['g', 'h', 'i'], 'targ_c': ['j', 'k', 'l'],
 '__builtins__': ,
 '__doc__': None, '__package__': None,
 '__loader__': ,
 'targ_a': ['a', 'b', 'c'], '__name__': '__main__',
 'targ_b': ['d', 'e', 'f'], '__spec__': None, 'value': 'a'}

as you can see, globals() returns a dictionary. Its keys are the names of the variables defined in the global namespace. Its values are the value held by each such variable.

Therefore

>>> next(n for n,v in filter(lambda t: isinstance(t[1],list) and t[0].startswith('targ_'), globals().items()) if value in v)
'targ_a'

iterates once on the generator produced by the expression, which yields each name in the global namespace that corresponds to a list whose name starts with targ_ and that contains an element equal to value. It does so by iterating on the dictionary returned by the call to globals