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‎Section 12/Comprehensions/challenge2-challenges.py‎

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# Create a comprehension that returns a list of all the locations that have an exit to the forest.
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# The list should contain the description of each location, if it's possible to get to the forest from there.
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#
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# The forest is location 5 in the locations dictionary
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# The exits for each location are represented by the exits dictionary.
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#
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# Remember that a dictionary has a .values() method, to return a list of the values.
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#
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# The forest can be reached from the road, and the hill; so those should be the descriptions that appear in your list.
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#
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# Test your program with different destinations (such as 1 for the road) to make sure it works.
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#
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# Once it's working, modify the program so that the comprehension returns a list of tuples.
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# Each tuple consists of the location number and the description.
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#
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# Finally, wrap your comprehension in a for loop, and print the lists of all the locations that lead to each of the
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# other locations in turn.
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# In other words, use a for loop to run the comprehension for each of the keys in the locations dictionary.
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locations = {0: "You are sitting in front of a computer learning Python",
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1: "You are standing at the end of a road before a small brick building",
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2: "You are at the top of a hill",
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3: "You are inside a building, a well house for a small stream",
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4: "You are in a valley beside a stream",
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5: "You are in the forest"}
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exits = {0: {"Q": 0},
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1: {"W": 2, "E": 3, "N": 5, "S": 4, "Q": 0},
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2: {"N": 5, "Q": 0},
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3: {"W": 1, "Q": 0},
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4: {"N": 1, "W": 2, "Q": 0},
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5: {"W": 2, "S": 1, "Q": 0}}
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# the_forest = [(key, locations[key]) for key, value in exits.items() if 5 in value.values()]
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# print(the_forest)
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for key_loc, value_loc in locations.items():
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the_forest = [(key, locations[key]) for key, value in exits.items() if key_loc in value.values()]
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print(f"Location number {key_loc}\n\t{the_forest}")
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# for key, value in exits.items():
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# if 5 in value.values():
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# print(f"Key: {key}, Desc: {locations[key]}")
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#
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# print(value.values())
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# print(f"Key: {key}\t|\tValue: {value}")
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# for key2, value2 in value.items():
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# print(f"\tKey2: {key2}\t|\tValue2: {value2}")
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# the_forest = [value for key, value in exits.items() if key == 5]
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# print(the_forest)
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# meals = [meal for meal in menu if "spam" not in meal and "chicken" not in meal]
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# print(meals)
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# for key, value in available_parts.items():

‎Section 12/Comprehensions/compchallenge2b.py‎

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locations = {0: "You are sitting in front of a computer learning Python",
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1: "You are standing at the end of a road before a small brick building",
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2: "You are at the top of a hill",
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3: "You are inside a building, a well house for a small stream",
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4: "You are in a valley beside a stream",
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5: "You are in the forest"}
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exits = {0: {"Q": 0},
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1: {"W": 2, "E": 3, "N": 5, "S": 4, "Q": 0},
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2: {"N": 5, "Q": 0},
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3: {"W": 1, "Q": 0},
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4: {"N": 1, "W": 2, "Q": 0},
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5: {"W": 2, "S": 1, "Q": 0}}
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print("nested for loops")
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print("---")
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for loc in sorted(locations):
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exits_to_destination_1 = []
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for ext in exits:
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if loc in exits[ext].values():
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exits_to_destination_1.append((ext, locations[ext]))
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print(f"Location leading to {loc}", end='\t')
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print(exits_to_destination_1)
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print("---")
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print("List comprehension inside a for loop")
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print("---")
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for loc in sorted(locations):
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exits_to_destination_2 = [(ext, locations[ext]) for ext in exits if loc in exits[ext].values()]
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print(f"Location leading to {loc}", end='\t')
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print(exits_to_destination_2)
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print("---")
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print("Nested comprehension")
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print("---")
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exits_to_destination_3 = [[(ext, locations[ext]) for ext in exits if loc in exits[ext].values()]
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for loc in sorted(locations)]
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print(exits_to_destination_3)
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print("---")
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for index, loc in enumerate(exits_to_destination_3):
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print(f"Location leading to {index}", end='\t')
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print(loc)

‎Section 12/Comprehensions/compchallenge2b_2.py‎

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import timeit
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setup = """\
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locations = {0: "You are sitting in front of a computer learning Python",
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1: "You are standing at the end of a road before a small brick building",
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2: "You are at the top of a hill",
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3: "You are inside a building, a well house for a small stream",
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4: "You are in a valley beside a stream",
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5: "You are in the forest"}
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exits = {0: {"Q": 0},
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1: {"W": 2, "E": 3, "N": 5, "S": 4, "Q": 0},
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2: {"N": 5, "Q": 0},
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3: {"W": 1, "Q": 0},
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4: {"N": 1, "W": 2, "Q": 0},
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5: {"W": 2, "S": 1, "Q": 0}}
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"""
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print("nested for loops")
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print("---")
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nested_loop = """\
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for loc in sorted(locations):
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exits_to_destination_1 = []
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for ext in exits:
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if loc in exits[ext].values():
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exits_to_destination_1.append((ext, locations[ext]))
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print(f"Location leading to {loc}", end='\t')
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print(exits_to_destination_1)
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"""
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print("---")
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print("List comprehension inside a for loop")
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print("---")
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loop_comp = """\
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for loc in sorted(locations):
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exits_to_destination_2 = [(ext, locations[ext]) for ext in exits if loc in exits[ext].values()]
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print(f"Location leading to {loc}", end='\t')
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print(exits_to_destination_2)
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"""
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print("---")
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print("Nested comprehension")
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print("---")
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nested_comp = """\
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exits_to_destination_3 = [[(ext, locations[ext]) for ext in exits if loc in exits[ext].values()]
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for loc in sorted(locations)]
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for index, loc in enumerate(exits_to_destination_3):
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print(f"Location leading to {index}", end='\t')
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print(loc)
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"""
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result_1 = timeit.timeit(nested_loop, setup, number=100000)
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result_2 = timeit.timeit(loop_comp, setup, number=100000)
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result_3 = timeit.timeit(nested_comp, setup, number=100000)
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print(f"Nested loop:\t{result_1}")
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print(f"Loop and comp:\t{result_2}")
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print(f"Nested comp:\t{result_3}")

‎Section 12/Comprehensions/compchallenge2b_3.py‎

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import timeit
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setup = """\
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gc.enable()
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locations = {0: "You are sitting in front of a computer learning Python",
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1: "You are standing at the end of a road before a small brick building",
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2: "You are at the top of a hill",
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3: "You are inside a building, a well house for a small stream",
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4: "You are in a valley beside a stream",
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5: "You are in the forest"}
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exits = {0: {"Q": 0},
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1: {"W": 2, "E": 3, "N": 5, "S": 4, "Q": 0},
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2: {"N": 5, "Q": 0},
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3: {"W": 1, "Q": 0},
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4: {"N": 1, "W": 2, "Q": 0},
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5: {"W": 2, "S": 1, "Q": 0}}
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"""
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locations = {0: "You are sitting in front of a computer learning Python",
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1: "You are standing at the end of a road before a small brick building",
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2: "You are at the top of a hill",
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3: "You are inside a building, a well house for a small stream",
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4: "You are in a valley beside a stream",
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5: "You are in the forest"}
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exits = {0: {"Q": 0},
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1: {"W": 2, "E": 3, "N": 5, "S": 4, "Q": 0},
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2: {"N": 5, "Q": 0},
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3: {"W": 1, "Q": 0},
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4: {"N": 1, "W": 2, "Q": 0},
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5: {"W": 2, "S": 1, "Q": 0}}
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def nested_loop():
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result = []
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for loc in sorted(locations):
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exits_to_destination_1 = []
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for ext in exits:
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if loc in exits[ext].values():
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exits_to_destination_1.append((ext, locations[ext]))
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result.append(exits_to_destination_1)
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# print the result before returning
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for x in result:
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pass
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return result
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print("---")
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def loop_comp():
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result = []
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for loc in sorted(locations):
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exits_to_destination_2 = [(ext, locations[ext]) for ext in exits if loc in exits[ext].values()]
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result.append(exits_to_destination_2)
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# print the result before returning
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for x in result:
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pass
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return result
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print("---")
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def nested_comp():
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exits_to_destination_3 = [[(ext, locations[ext]) for ext in exits if loc in exits[ext].values()]
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for loc in sorted(locations)]
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# print the result before returning
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for x in exits_to_destination_3:
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pass
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return exits_to_destination_3
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def nested_gen():
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exits_to_destination_3 = ([(ext, locations[ext]) for ext in exits if loc in exits[ext].values()]
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for loc in sorted(locations))
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# print the result before returning
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for x in exits_to_destination_3:
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pass
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return exits_to_destination_3
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# print(nested_loop())
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# print(loop_comp())
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# print(nested_comp())
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result_1 = timeit.timeit(nested_loop, setup, number=100000)
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result_2 = timeit.timeit(loop_comp, setup, number=100000)
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result_3 = timeit.timeit(nested_comp, setup, number=100000)
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result_4 = timeit.timeit(nested_gen, setup, number=100000)
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print(f"Nested loop:\t{result_1}")
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print(f"Loop and comp:\t{result_2}")
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print(f"Nested comp:\t{result_3}")
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print(f"Nested gen:\t\t{result_4}")

‎Section 12/Comprehensions/fizzbuzz.py‎

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# Create a new Python file - I've called this one "fizzbuzz.py".
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#
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# Use the conditional expression from the previous video to produce
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# a list comprehension that returns the fizzbuzz results.
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#
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# If a number's divisible by 3, the value should be "fizz".
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# If it's divisible by 5, the value should be "buzz".
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# If it's divisible by both 3 and 5, the value should be "fizz buzz"
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# Finally, if none of those conditions apply, the value will be the number itself.
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#
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# The code from the end of the last video appears below, so you can check the result.
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for x in range(1, 31):
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fizzbuzz = "fizz buzz" if x % 15 == 0 else "fizz" if x % 3 == 0 else "buzz" if x % 5 == 0 else str(x)
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print(fizzbuzz)
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fizz_list = ["fizz buzz" if x % 15 == 0 else "fizz" if x % 3 == 0 else "buzz" if x % 5 == 0 else str(x)
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for x in range(1, 31)]
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print(fizz_list)

‎Section 12/Comprehensions/nested1.py‎

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burgers = ["beef", "chicken", "spicy bean"]
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toppings = {"cheese", "egg", "beans", "spam"}
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meals = [(burger, topping) for burger in burgers for topping in toppings]
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print(meals)
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print("---")
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for meals in [(burger, topping) for burger in burgers for topping in toppings]:
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print(meals)
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print("---")
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for burger in burgers:
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for topping in toppings:
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print((burger, topping))
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print("---")
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for nested_meals in [[(burger, topping) for burger in burgers] for topping in toppings]:
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print(nested_meals)
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print("---")
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for nested_meals in [[(burger, topping) for topping in toppings] for burger in burgers]:
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print(nested_meals)

‎Section 12/Comprehensions/nested_challenge.py‎

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# In an early video, we used a for loop to print the times tables, for values from 1 to 10.
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# That was a nested loop, which appears below.
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#
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# The challenge is to use a nested comprehension, to produce the same values.
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# You can iterate over the list, to produce the same output as the for loop, or just print out the list.
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for i in range(1, 11):
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for j in range(1, 11):
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print(i, i * j)
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i_range = range(1, 11)
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j_range = range(1, 11)
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nested_numbers = [[(i, i * j) for j in j_range] for i in i_range]
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print(nested_numbers)
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print("---")
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times = [(i, i * j) for i in range(1, 11) for j in range(1, 11)]
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print(times)
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print("---")
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for x, y in [(i, i * j) for i in range(1, 11) for j in range(1, 11)]:
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print(x, y)

‎Section 12/Comprehensions/timeitchallenge.py‎

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# In the section on Functions, we looked at 2 different ways to calculate the factorial
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# of a number. We used an iterative approach, and also used a recursive function.
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#
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# This challenge is to use the timeit module to see which performs better.
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#
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# The two functions appear below.
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#
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# Hint: change the number of iterations to 1,000 or 10,000. The default
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# of one million will take a long time to run.
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import timeit
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fact_test = """\
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def fact(n):
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result = 1
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if n > 1:
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for f in range(2, n + 1):
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result *= f
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return result
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x = fact(130)
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"""
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factorial_test = """\
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def factorial(n):
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# n! can also be defined as n * (n-1)!
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if n <= 1:
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return 1
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else:
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return n * factorial(n-1)
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y = factorial(130)
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"""
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print(timeit.timeit(fact_test, number=10000))
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print(timeit.timeit(factorial_test, number=10000))

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