davgit
diff --git a/‎conversions/bin_to_octal.py‎
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+"""
+The function below will convert any binary string to the octal equivalent.
+
+>>> bin_to_octal("1111")
+'17'
+
+>>> bin_to_octal("101010101010011")
+'52523'
+
+>>> bin_to_octal("")
+Traceback (most recent call last):
+...
+ValueError: Empty string was passed to the function
+>>> bin_to_octal("a-1")
+Traceback (most recent call last):
+...
+ValueError: Non-binary value was passed to the function
+"""
+
+
+def bin_to_octal(bin_string: str) -> str:
+    if not all(char in "01" for char in bin_string):
+        raise ValueError("Non-binary value was passed to the function")
+    if not bin_string:
+        raise ValueError("Empty string was passed to the function")
+    oct_string = ""
+    while len(bin_string) % 3 != 0:
+        bin_string = "0" + bin_string
+    bin_string_in_3_list = [
+        bin_string[index: index + 3]
+        for index, value in enumerate(bin_string)
+        if index % 3 == 0
+    ]
+    for bin_group in bin_string_in_3_list:
+        oct_val = 0
+        for index, val in enumerate(bin_group):
+            oct_val += int(2 ** (2 - index) * int(val))
+        oct_string += str(oct_val)
+    return oct_string
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()