##Pyke (commit 31), 10 9 bytes

=blR.fbtp

Explanation:

=b         -    set characters for base conversion to eval_or_not(input())
  l        -   len(^)
   R      -  [^, eval_or_not(input()]
    .f    - first_n(^)
      b   -    conv_base(^)
       t  -   ^[-1]
        p -  print(^)

Pyke (commit 31), 10 9 bytes

=blR.fbtp

Explanation:

=b         -    set characters for base conversion to eval_or_not(input())
  l        -   len(^)
   R      -  [^, eval_or_not(input()]
    .f    - first_n(^)
      b   -    conv_base(^)
       t  -   ^[-1]
        p -  print(^)

##Pyke (commit 31), 10 bytes

=blQR.fbtp

Explanation:

           - autoassign Q = eval_or_not(input())
=b         -    set characters for base conversion to eval_or_not(input())
  l        -   len(^)
   QR      -  [Q, ^]
     .f    - first_n(^)
       b   -    conv_base(^)
        t  -   ^[-1]
         p -  print(^)

##Pyke (commit 31), 10 9 bytes

=blR.fbtp

Explanation:

=b         -    set characters for base conversion to eval_or_not(input())
  l        -   len(^)
   R      -  [^, eval_or_not(input()]
    .f    - first_n(^)
      b   -    conv_base(^)
       t  -   ^[-1]
        p -  print(^)