Bit manipulation: add type hints, validation, doctests; simplify bitwise operations

Author: Poortigupta

bit_manipulation/binary_and_operator.py

@@ -1,49 +1,48 @@
+"""Bitwise AND helper.
+
+Return a zero-padded binary string representing ``a & b`` where the width is the
+maximum bit length of the inputs. Only non-negative integers are accepted.
+
+>>> binary_and(25, 32)
+'0b000000'
+>>> binary_and(37, 50)
+'0b100000'
+>>> binary_and(21, 30)
+'0b10100'
+>>> binary_and(58, 73)
+'0b0001000'
+>>> binary_and(0, 255)
+'0b00000000'
+>>> binary_and(256, 256)
+'0b100000000'
+
+Invalid inputs raise clear exceptions:
+
+>>> binary_and(0, -1)
+Traceback (most recent call last):
+    ...
+ValueError: inputs must be non-negative integers
+>>> binary_and(0, 1.1)
+Traceback (most recent call last):
+    ...
+TypeError: inputs must be integers
+>>> binary_and("0", "1")
+Traceback (most recent call last):
+    ...
+TypeError: inputs must be integers
+"""
+
 # https://www.tutorialspoint.com/python3/bitwise_operators_example.htm
 
 
 def binary_and(a: int, b: int) -> str:
-    """
-    Take in 2 integers, convert them to binary,
-    return a binary number that is the
-    result of a binary and operation on the integers provided.
-
-    >>> binary_and(25, 32)
-    '0b000000'
-    >>> binary_and(37, 50)
-    '0b100000'
-    >>> binary_and(21, 30)
-    '0b10100'
-    >>> binary_and(58, 73)
-    '0b0001000'
-    >>> binary_and(0, 255)
-    '0b00000000'
-    >>> binary_and(256, 256)
-    '0b100000000'
-    >>> binary_and(0, -1)
-    Traceback (most recent call last):
-        ...
-    ValueError: the value of both inputs must be positive
-    >>> binary_and(0, 1.1)
-    Traceback (most recent call last):
-        ...
-    ValueError: Unknown format code 'b' for object of type 'float'
-    >>> binary_and("0", "1")
-    Traceback (most recent call last):
-        ...
-    TypeError: '<' not supported between instances of 'str' and 'int'
-    """
+    if not isinstance(a, int) or not isinstance(b, int):
+        raise TypeError("inputs must be integers")
     if a < 0 or b < 0:
-        raise ValueError("the value of both inputs must be positive")
-
-    a_binary = format(a, "b")
-    b_binary = format(b, "b")
-
-    max_len = max(len(a_binary), len(b_binary))
+        raise ValueError("inputs must be non-negative integers")
 
-    return "0b" + "".join(
-        str(int(char_a == "1" and char_b == "1"))
-        for char_a, char_b in zip(a_binary.zfill(max_len), b_binary.zfill(max_len))
-    )
+    max_len = max(a.bit_length(), b.bit_length())
+    return f"0b{(a & b):0{max_len}b}"
 
 
 if __name__ == "__main__":

bit_manipulation/binary_or_operator.py

@@ -1,45 +1,47 @@
+"""Bitwise OR helper.
+
+Return a zero-padded binary string representing ``a | b`` where the width is the
+maximum bit length of the inputs. Only non-negative integers are accepted.
+
+>>> binary_or(25, 32)
+'0b111001'
+>>> binary_or(37, 50)
+'0b110111'
+>>> binary_or(21, 30)
+'0b11111'
+>>> binary_or(58, 73)
+'0b1111011'
+>>> binary_or(0, 255)
+'0b11111111'
+>>> binary_or(0, 256)
+'0b100000000'
+
+Invalid inputs raise clear exceptions:
+
+>>> binary_or(0, -1)
+Traceback (most recent call last):
+    ...
+ValueError: inputs must be non-negative integers
+>>> binary_or(0, 1.1)
+Traceback (most recent call last):
+    ...
+TypeError: inputs must be integers
+>>> binary_or("0", "1")
+Traceback (most recent call last):
+    ...
+TypeError: inputs must be integers
+"""
+
 # https://www.tutorialspoint.com/python3/bitwise_operators_example.htm
 
 
 def binary_or(a: int, b: int) -> str:
-    """
-    Take in 2 integers, convert them to binary, and return a binary number that is the
-    result of a binary or operation on the integers provided.
-
-    >>> binary_or(25, 32)
-    '0b111001'
-    >>> binary_or(37, 50)
-    '0b110111'
-    >>> binary_or(21, 30)
-    '0b11111'
-    >>> binary_or(58, 73)
-    '0b1111011'
-    >>> binary_or(0, 255)
-    '0b11111111'
-    >>> binary_or(0, 256)
-    '0b100000000'
-    >>> binary_or(0, -1)
-    Traceback (most recent call last):
-        ...
-    ValueError: the value of both inputs must be positive
-    >>> binary_or(0, 1.1)
-    Traceback (most recent call last):
-        ...
-    TypeError: 'float' object cannot be interpreted as an integer
-    >>> binary_or("0", "1")
-    Traceback (most recent call last):
-        ...
-    TypeError: '<' not supported between instances of 'str' and 'int'
-    """
+    if not isinstance(a, int) or not isinstance(b, int):
+        raise TypeError("inputs must be integers")
     if a < 0 or b < 0:
-        raise ValueError("the value of both inputs must be positive")
-    a_binary = str(bin(a))[2:]  # remove the leading "0b"
-    b_binary = str(bin(b))[2:]
-    max_len = max(len(a_binary), len(b_binary))
-    return "0b" + "".join(
-        str(int("1" in (char_a, char_b)))
-        for char_a, char_b in zip(a_binary.zfill(max_len), b_binary.zfill(max_len))
-    )
+        raise ValueError("inputs must be non-negative integers")
+    max_len = max(a.bit_length(), b.bit_length())
+    return f"0b{(a | b):0{max_len}b}"
 
 
 if __name__ == "__main__":

bit_manipulation/binary_xor_operator.py

@@ -1,49 +1,48 @@
+"""Bitwise XOR helper.
+
+Return a zero-padded binary string representing ``a ^ b`` where the width is the
+maximum bit length of the inputs. Only non-negative integers are accepted.
+
+>>> binary_xor(25, 32)
+'0b111001'
+>>> binary_xor(37, 50)
+'0b010111'
+>>> binary_xor(21, 30)
+'0b01011'
+>>> binary_xor(58, 73)
+'0b1110011'
+>>> binary_xor(0, 255)
+'0b11111111'
+>>> binary_xor(256, 256)
+'0b000000000'
+
+Invalid inputs raise clear exceptions:
+
+>>> binary_xor(0, -1)
+Traceback (most recent call last):
+    ...
+ValueError: inputs must be non-negative integers
+>>> binary_xor(0, 1.1)
+Traceback (most recent call last):
+    ...
+TypeError: inputs must be integers
+>>> binary_xor("0", "1")
+Traceback (most recent call last):
+    ...
+TypeError: inputs must be integers
+"""
+
 # https://www.tutorialspoint.com/python3/bitwise_operators_example.htm
 
 
 def binary_xor(a: int, b: int) -> str:
-    """
-    Take in 2 integers, convert them to binary,
-    return a binary number that is the
-    result of a binary xor operation on the integers provided.
-
-    >>> binary_xor(25, 32)
-    '0b111001'
-    >>> binary_xor(37, 50)
-    '0b010111'
-    >>> binary_xor(21, 30)
-    '0b01011'
-    >>> binary_xor(58, 73)
-    '0b1110011'
-    >>> binary_xor(0, 255)
-    '0b11111111'
-    >>> binary_xor(256, 256)
-    '0b000000000'
-    >>> binary_xor(0, -1)
-    Traceback (most recent call last):
-        ...
-    ValueError: the value of both inputs must be positive
-    >>> binary_xor(0, 1.1)
-    Traceback (most recent call last):
-        ...
-    TypeError: 'float' object cannot be interpreted as an integer
-    >>> binary_xor("0", "1")
-    Traceback (most recent call last):
-        ...
-    TypeError: '<' not supported between instances of 'str' and 'int'
-    """
+    if not isinstance(a, int) or not isinstance(b, int):
+        raise TypeError("inputs must be integers")
     if a < 0 or b < 0:
-        raise ValueError("the value of both inputs must be positive")
-
-    a_binary = str(bin(a))[2:]  # remove the leading "0b"
-    b_binary = str(bin(b))[2:]  # remove the leading "0b"
-
-    max_len = max(len(a_binary), len(b_binary))
+        raise ValueError("inputs must be non-negative integers")
 
-    return "0b" + "".join(
-        str(int(char_a != char_b))
-        for char_a, char_b in zip(a_binary.zfill(max_len), b_binary.zfill(max_len))
-    )
+    max_len = max(a.bit_length(), b.bit_length())
+    return f"0b{(a ^ b):0{max_len}b}"
 
 
 if __name__ == "__main__":

bit_manipulation/is_even.py

@@ -1,17 +1,9 @@
 def is_even(number: int) -> bool:
-    """
-    return true if the input integer is even
-    Explanation: Lets take a look at the following decimal to binary conversions
-    2 => 10
-    14 => 1110
-    100 => 1100100
-    3 => 11
-    13 => 1101
-    101 => 1100101
-    from the above examples we can observe that
-    for all the odd integers there is always 1 set bit at the end
-    also, 1 in binary can be represented as 001, 00001, or 0000001
-    so for any odd integer n => n&1 is always equals 1 else the integer is even
+    """Return True if the input integer is even using a bitwise check.
+
+    Explanation:
+    In binary, even numbers always have the least significant bit cleared (0),
+    while odd numbers have it set (1). Therefore, ``n & 1 == 0`` implies even.
 
     >>> is_even(1)
     False
@@ -27,8 +19,19 @@ def is_even(number: int) -> bool:
     True
     >>> is_even(101)
     False
+    >>> is_even(True)
+    Traceback (most recent call last):
+        ...
+    TypeError: input must be an integer
+    >>> is_even(3.14)
+    Traceback (most recent call last):
+        ...
+    TypeError: input must be an integer
     """
-    return number & 1 == 0
+    if not isinstance(number, int) or isinstance(number, bool):
+        # bool is a subclass of int; explicitly disallow it as a number here.
+        raise TypeError("input must be an integer")
+    return (number & 1) == 0
 
 
 if __name__ == "__main__":