Solution to problem 4 in Python

src/Year_2015/P4.py

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+# --- Day 4: The Ideal Stocking Stuffer ---
+
+# Santa needs help mining some AdventCoins (very similar to bitcoins) to use as
+# gifts for all the economically forward-thinking little girls and boys.
+
+# To do this, he needs to find MD5 hashes which, in hexadecimal, start with at
+# least five zeroes. The input to the MD5 hash is some secret key (your puzzle
+# input, given below) followed by a number in decimal. To mine AdventCoins, you
+# must find Santa the lowest positive number (no leading zeroes: 1, 2, 3, ...)
+# that produces such a hash.
+
+# For example:
+
+#     If your secret key is abcdef, the answer is 609043, because the MD5 hash
+# of abcdef609043 starts with five zeroes (000001dbbfa...), and it is the
+# lowest such number to do so.
+#     If your secret key is pqrstuv, the lowest number it combines with to make
+# an MD5 hash starting with five zeroes is 1048970; that is, the MD5 hash of
+# pqrstuv1048970 looks like 000006136ef....
+
+# Your puzzle input is yzbqklnj.
+
+from hashlib import md5
+
+_input = "yzbqklnj"
+
+
+def part_1() -> None:
+    end = "9" * len(_input)
+    for num in range(int(end)):
+        testing = _input + str(num)
+        result = md5(testing.encode()).hexdigest()
+        if result.startswith("0" * 5):
+            print(f"The lowest positive number is {num}")
+            break
+
+
+# --- Part Two ---
+
+# Now find one that starts with six zeroes.
+
+
+def part_2() -> None:
+    end = "9" * len(_input)
+    for num in range(int(end)):
+        testing = _input + str(num)
+        result = md5(testing.encode()).hexdigest()
+        if result.startswith("0" * 6):
+            print(f"The lowest positive number is {num}")
+            break
+
+
+if __name__ == "__main__":
+    part_1()
+    part_2()