I wrote a docstring in each function about what that function does.

When I was writing the docstring I was thinking about how to explain it rather than trying to make sure the program is working.
I might use a doctring in my suture projects to make sure that I know what the function is for in case I need to go back and fix things.

yahtzee.py

@@ -5,34 +5,39 @@ class Yahtzee:
     This version of Yahtzee is initialized with a list of goals.
     """
     def __init__(self, goals):
-        self.score = 0
-        self.goals = goals
-        self.dice = [Die() for num in range(5)]
+     """Sets up the game with goals, score, and 5 dice."""   
+     self.score = 0
+     self.goals = goals
+     self.dice = [Die() for num in range(5)]
 
     def play(self):
-        print("Welcome to Yachtzee!")
-        self.score = 0
-        for goal in self.goals:
-            goal.used = False
-        while self.count_unused_goals() > 0:
-            self.play_round()
-        print(f"Your final score was {self.score}")
+     """Play the entire game until all goals are used."""   
+    print("Welcome to Yachtzee!")
+    self.score = 0
+    for goal in self.goals:
+        goal.used = False
+    while self.count_unused_goals() > 0:
+         self.play_round()
+    print(f"Your final score was {self.score}")
 
     def play_round(self):
-        print("=" * 80)
-        self.rolls_left = 3
-        for die in self.dice:
+       """Play one round: roll dice, choose a goal and make a score."""
+    print("=" * 80)
+    self.rolls_left = 3
+    for die in self.dice:
             die.roll()
-        self.show_status()
-        goal = self.choose_goal()
-        goal.used = True
-        self.score += goal.score(self.dice)
+    self.show_status()
+    goal = self.choose_goal()
+    goal.used = True
+    self.score += goal.score(self.dice)
 
     def show_status(self):
+        """Shows the recent score."""
         dice = ', '.join([str(die) for die in self.dice])
         print(f"Score: {self.score}. Rolls left: {self.rolls_left}. Dice: {dice}.")
 
     def choose_goal(self):
+        """Players should pick a goal or roll again."""
         options = []
         unused_goals = self.get_unused_goals()
         for goal in unused_goals:
@@ -49,6 +54,7 @@ class Yahtzee:
             return unused_goals[choice]
 
     def get_choice(self, options):
+        """Players get to choose an option."""
         print("What would you like to do?")
         for i, option in enumerate(options):
             print(f"{i}. {option}")
@@ -59,6 +65,7 @@ class Yahtzee:
         return int(choice)
 
     def option_choice_is_valid(self, choice, options):
+        """Checks if the choice made is correct."""
         if not choice.isdigit():
             return False
         if int(choice) < 0:
@@ -71,6 +78,7 @@ class Yahtzee:
         return len(self.get_unused_goals())
 
     def get_unused_goals(self):
+        """Players get back there unused goals."""
         unused_goals = []
         for goal in self.goals:
             if not goal.used:
@@ -78,6 +86,7 @@ class Yahtzee:
         return unused_goals
 
     def reroll(self):
+        """Players get to roll the dice."""
         self.rolls_left -= 1
         choices = self.get_reroll_choices()
         dice_to_reroll = self.get_dice_to_reroll(choices)
@@ -85,6 +94,7 @@ class Yahtzee:
             die.roll()
 
     def get_dice_to_reroll(self, choice_ints):
+        """Players get to re-roll there dice based on there choice."""
         dice_to_reroll = []
         for die in self.dice:
             if die.face in choice_ints:
@@ -93,6 +103,7 @@ class Yahtzee:
         return dice_to_reroll
 
     def get_reroll_choices(self):
+        """Gives players options on which dice to re-roll."""
         print("Which dice do you want to re-roll?")
         choices = input("> ")
         while not self.reroll_choices_are_valid(choices):
@@ -102,6 +113,7 @@ class Yahtzee:
         return choice_ints
         
     def reroll_choices_are_valid(self, choices_str):
+        """Checks if the re-roll dice are correct."""
         if not choices_str.isdigit():
             return False
         choice_ints = [int(digit) for digit in choices_str]