Solution to problem 4 part 1 in Python

src/Year_2017/P4.py

@@ -0,0 +1,33 @@
+# --- Day 4: High-Entropy Passphrases ---
+
+# A new system policy has been put in place that requires all accounts to use a
+# passphrase instead of simply a password. A passphrase consists of a series of
+# words (lowercase letters) separated by spaces.
+
+# To ensure security, a valid passphrase must contain no duplicate words.
+
+# For example:
+
+#     aa bb cc dd ee is valid.
+#     aa bb cc dd aa is not valid - the word aa appears more than once.
+#     aa bb cc dd aaa is valid - aa and aaa count as different words.
+
+# The system's full passphrase list is available as your puzzle input. How many
+# passphrases are valid?
+
+with open("files/P4.txt") as f:
+    passphrase_list = [line for line in f.read().strip().split("\n")]
+
+
+def part_1() -> None:
+    valid = sum(
+        1
+        for passphrase in passphrase_list
+        if len(passphrase.split()) == len(set(passphrase.split()))
+    )
+
+    print(f"There are {valid} valid passphrases")
+
+
+if __name__ == "__main__":
+    part_1()