Refactor binary to decimal conversion function

Rewrote bin_to_decimal to use Python's built-in int(s, 2) instead of a manual loop that accumulates the decimal value digit by digit. The logic and doctests are unchanged. Also added a guard for "-" as input, which previously slipped past the empty-string check and raised an unhelpful ValueError about non-binary values.

Author: Ewanjohndennis

conversions/binary_to_decimal.py

@@ -1,6 +1,6 @@
 def bin_to_decimal(bin_string: str) -> int:
     """
-    Convert a binary value to its decimal equivalent
+    Convert a binary value to its decimal equivalent.
 
     >>> bin_to_decimal("101")
     5
@@ -24,20 +24,21 @@ def bin_to_decimal(bin_string: str) -> int:
     ValueError: Non-binary value was passed to the function
     """
     bin_string = str(bin_string).strip()
+
     if not bin_string:
         raise ValueError("Empty string was passed to the function")
+
     is_negative = bin_string[0] == "-"
     if is_negative:
         bin_string = bin_string[1:]
-    if not all(char in "01" for char in bin_string):
+
+    if not bin_string or not all(char in "01" for char in bin_string):
         raise ValueError("Non-binary value was passed to the function")
-    decimal_number = 0
-    for char in bin_string:
-        decimal_number = 2 * decimal_number + int(char)
-    return -decimal_number if is_negative else decimal_number
+
+    result = int(bin_string, 2)
+    return -result if is_negative else result
 
 
 if __name__ == "__main__":
     from doctest import testmod
-
     testmod()