Hacktoberfest: Added Octal Number to Hexadecimal Number Conversion Algorithm (#10533)

* Added Octal to Hexadecimal Conversion program under 'conversions' directory

* Update conversions/octal_to_hexadecimal.py

fix: minor improvement to directly return hexadecimal value

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update conversions/octal_to_hexadecimal.py

fix: improvement updates to octal to hexadecimal

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update conversions/octal_to_hexadecimal.py

fix: Readablility improvements to octal to hexadecimal convertor

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update conversions/octal_to_hexadecimal.py

fix: readability improvements in octal_to_hexadecimal.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update conversions/octal_to_hexadecimal.py

fix: readability improvements in octal_to_hexadecimal.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* fix: Fixed all the errors in octal_to_hexadecimal.py after commiting suggested changes

* fix: modified the prefix of hex numbers to the '0x' standard in octal_to_hexadecimal.py

---------

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

conversions/octal_to_hexadecimal.py

@@ -0,0 +1,65 @@
+def octal_to_hex(octal: str) -> str:
+    """
+    Convert an Octal number to Hexadecimal number.
+    For more information: https://en.wikipedia.org/wiki/Octal
+
+    >>> octal_to_hex("100")
+    '0x40'
+    >>> octal_to_hex("235")
+    '0x9D'
+    >>> octal_to_hex(17)
+    Traceback (most recent call last):
+        ...
+    TypeError: Expected a string as input
+    >>> octal_to_hex("Av")
+    Traceback (most recent call last):
+        ...
+    ValueError: Not a Valid Octal Number
+    >>> octal_to_hex("")
+    Traceback (most recent call last):
+        ...
+    ValueError: Empty string was passed to the function
+    """
+
+    if not isinstance(octal, str):
+        raise TypeError("Expected a string as input")
+    if octal.startswith("0o"):
+        octal = octal[2:]
+    if octal == "":
+        raise ValueError("Empty string was passed to the function")
+    if any(char not in "01234567" for char in octal):
+        raise ValueError("Not a Valid Octal Number")
+
+    decimal = 0
+    for char in octal:
+        decimal <<= 3
+        decimal |= int(char)
+
+    hex_char = "0123456789ABCDEF"
+
+    revhex = ""
+    while decimal:
+        revhex += hex_char[decimal & 15]
+        decimal >>= 4
+
+    return "0x" + revhex[::-1]
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+
+    nums = ["030", "100", "247", "235", "007"]
+
+    ## Main Tests
+
+    for num in nums:
+        hexadecimal = octal_to_hex(num)
+        expected = "0x" + hex(int(num, 8))[2:].upper()
+
+        assert hexadecimal == expected
+
+        print(f"Hex of '0o{num}' is: {hexadecimal}")
+        print(f"Expected was: {expected}")
+        print("---")