How to get single '\' (backslash) printed by a function?

I am trying to print something with a function in python using Jupyter notebook. As an example, let's say I want a function that prints '\x' where 'x' is the argument of the function.

def mu():
    a="\\"
    b="mu_"
    return (a+b)

This should give me '\mu_' as the output. But it is giving me '\\mu_' as output. I had tried with single '\' first, but there was an error. I found an answer for that problem here in the stack overflow, which allows to print a single '\' by using the double backslash i.e.'\\' But that was for print() command only, and not inside a function. This doesn't work inside a function. Is there a way to make the above function work as I want and get a single '\' in the output as '\mu_'?

EDIT: This happens with any odd number of backslashes. But when I use even number of backslashes, I get back the same even number of backslashes. For odd number the error is:

  File "<ipython-input-25-e1de4609aed4>", line 2
a='\\\'
       ^
SyntaxError: EOL while scanning string literal

For the above error, I defined a = '\\\' inside the same function as above.

I hope I could express the issue clearly, if not please let me know in the comments.

P.S.- Please note that this question is not identical to some other questions here. The problem is particularly with the 'return' command used inside a function. I just realized that. If I use print(), it works as I want (which has been asked before in this platform.) but I want to know if it is possible to make it work using function.

Thus the narrowed down version of the problem has to do with the return command.

EDIT: It is essential for me to solve the problem using a function as I need to append this '\mu_' in an array. printing it is not enough. See the following code:

def ten(n,r):
    tiu = []
    for i in range(1,n+1):
        index = str(i)
        u = 'u^' + '\mu_' + index
        tiu.append(u)
    return (tiu)

In the next cell I type:

ten(4,1)

which gives the output:

['u^\\mu_1', 'u^\\mu_2', 'u^\\mu_3', 'u^\\mu_4']

Now if I use 2 '\' in the function, nothing changes in the output. But if I use 3 '\', I get 4 '\' in the outputs.

Solution

When printing a list in python the repr() method is called in the background. The string stored is '\', it's just represented as '\\'.

If you print out every element individually, it will show you the literal value as opposed to the represented value:

print(ten(4, 1)[1])

Output:

u^\mu_2