Add utility functions for list and dict operations

Week03/sequences_first_last.py

@@ -0,0 +1,32 @@
+def remove_duplicates(seq: list) -> list:
+    """
+    This function removes duplicates from a list.
+    """
+    unique = []
+    for item in seq:
+        if item not in unique:
+            unique.append(item)
+    return unique
+
+
+def list_counts(seq: list) -> dict:
+    """
+    This function counts the number of occurrences of each item in a list.
+    """
+    counts = {}
+    for item in seq:
+        if item in counts:
+            counts[item] += 1
+        else:
+            counts[item] = 1
+    return counts
+
+
+def reverse_dict(d: dict) -> dict:
+    """
+    This function reverses the keys and values of a dictionary.
+    """
+    reversed_d = {}
+    for key, value in d.items():
+        reversed_d[value] = key
+    return reversed_d