Exercises: Files

An arcade manager wants a score report whose first line clearly labels the numbers below it.

Specification: Define score_text_with_header(scores, path). First open path in "w" mode with a with statement. Write the fixed header line ARCADE SCORES with f.write(f"ARCADE SCORES\n"), then loop through scores and write one score per f-string line. After that file closes, open the same path with with open(path, "r") as f: and use f.read() to load the whole file. Return all the loaded text, including the header. Use ex1_scores.txt.

Worked sample calls:

score_text_with_header([45, 70, 55], "ex1_scores.txt") -> "ARCADE SCORES\n45\n70\n55\n"
score_text_with_header([120, 95], "ex1_scores.txt") -> "ARCADE SCORES\n120\n95\n"
score_text_with_header([300], "ex1_scores.txt") -> "ARCADE SCORES\n300\n"

A puzzle judge needs the saved score lines back as integers, not text.

Specification: Define score_list_round_trip(scores, path). First write every score to path, one per line, in "w" mode. Then make a new empty list, open the same path with with open(path, "r") as f:, and use for line in f:. Transform each line with int(line.strip()) and append the integer. Return the rebuilt list. Use ex2_score_list.txt.

Worked sample calls:

score_list_round_trip([18, 27, 36], "ex2_score_list.txt") -> [18, 27, 36]
score_list_round_trip([5, 105], "ex2_score_list.txt") -> [5, 105]
score_list_round_trip([42], "ex2_score_list.txt") -> [42]

A prize booth needs both the total number of saved tickets and the number of awards that reached a goal.

Specification: Define saved_ticket_report(tickets, target, path). First write every ticket number to path, one per line. Start total = 0 and count = 0, then open the same path with with open(path, "r") as f:. Use one for line in f: loop. Convert each line with int(line.strip()), add that number to total, and add 1 to count when the number is at least target. Return [total, count]. Do not build a loaded list and do not call sum. Use ex3_tickets.txt.

Worked sample calls:

saved_ticket_report([20, 35, 15], 25, "ex3_tickets.txt") -> [70, 1]
saved_ticket_report([100, 50], 50, "ex3_tickets.txt") -> [150, 2]
saved_ticket_report([9, 12, 7], 20, "ex3_tickets.txt") -> [28, 0]

A tournament screen needs the lowest score, highest score, total, and number of scores from one saved round.

Specification: Define saved_score_summary(scores, path). First write every score to path, one per line. Then build a new integer list by opening the same path with with open(path, "r") as f:, looping through its lines, changing each line with int(line.strip()), and appending it. Return [min(loaded), max(loaded), sum(loaded), len(loaded)]. The supplied list always has at least one score. Use ex4_summary.txt.

Worked sample calls:

saved_score_summary([8, 15, 11], "ex4_summary.txt") -> [8, 15, 34, 3]
saved_score_summary([50, 20], "ex4_summary.txt") -> [20, 50, 70, 2]
saved_score_summary([99], "ex4_summary.txt") -> [99, 99, 99, 1]

A scorekeeper wants to see the best result found so far while scanning a saved file.

Specification: Define highest_saved_score(scores, path). The supplied list always has at least one score. First write every score to path, one per line. Set best = scores[0], then open the same path with with open(path, "r") as f: and use for line in f:. Convert the cleaned line with int(line.strip()). If that score is greater than best, replace best. Return best. Do not call max. Use ex5_high_score.txt.

Worked sample calls:

highest_saved_score([44, 81, 63], "ex5_high_score.txt") -> 81
highest_saved_score([205, 199, 201], "ex5_high_score.txt") -> 205
highest_saved_score([17], "ex5_high_score.txt") -> 17

A league report needs one readable summary built from a saved name, level, and points.

Specification: Define player_record_summary(name, level, points, path). First write name, level, and points to path on three separate lines, using an f-string for each write. Then open the same path with with open(path, "r") as f:. Read the three saved lines in order with f.readline(). Strip the saved name and convert the saved level and points with int(...). Return an f-string in the exact form "name: level level, points points". Use ex6_typed_record.txt.

Worked sample calls:

player_record_summary("Lina", 3, 480, "ex6_typed_record.txt") -> "Lina: level 3, 480 points"
player_record_summary("Mateo", 5, 925, "ex6_typed_record.txt") -> "Mateo: level 5, 925 points"
player_record_summary("Zoe", 1, 75, "ex6_typed_record.txt") -> "Zoe: level 1, 75 points"

A check-in desk saves a roster with one player name per line, then checks the saved lines in order for an exact match.

Specification: Define save_and_find_player(names, target, path). First write every name to path, one per line, with f.write(f"{name}\n"). Then open the same path with with open(path, "r") as f:. Use exactly for line in f:, followed by if line.strip() == target: and an immediate return of f"Found {target}.". After the loop, return f"{target} was not found.". Do not load the whole file or use a text-membership search. Use ex7_roster.txt.

Worked sample calls:

save_and_find_player(["Inez", "Kai", "Noor"], "Inez", "ex7_roster.txt") -> "Found Inez."
save_and_find_player(["Inez", "Kai", "Noor"], "Noor", "ex7_roster.txt") -> "Found Noor."
save_and_find_player(["Inez", "Kai", "Noor"], "Pia", "ex7_roster.txt") -> "Pia was not found."

A late round arrives after the first scores have already been saved.

Specification: Define append_round_trip(scores, late_score, path). Write the original scores one per line with "w". Append the late score with a separate "a" block. Reload every line as an integer and return the list. Put a short purpose comment above the function. Use ex8_late_score.txt.

Worked sample calls:

append_round_trip([62, 48], 91, "ex8_late_score.txt") -> [62, 48, 91]

A tiny map must survive after the drawing program stops.

Specification: Define map_round_trip(rows, path). Write one row per line with "w", then reload each row with strip() and append it to a new list. Return the saved rows with no extra newlines. Put a short purpose comment above the function. Use ex9_map.txt.

Worked sample calls:

map_round_trip(["#.#", "...", "#.#"], "ex9_map.txt") -> ['#.#', '...', '#.#']

A score table stores each team and its points together on one comma-separated line.

Specification: Define best_team(records, path) for at least one record in "name,points" form. Every points value is 0 or more. Save the lines with "w", then reload them. For each line, use parts = line.strip().split(",") and int(parts[1]). Seed best_points = -1 and best_name = "". Update both only for strictly greater points; ties keep the first team. Return its name. Put a short purpose comment above the function. Use ex10_teams.txt.

Worked sample calls:

best_team(["Ivo,15", "Uma,9", "Teo,22"], "ex10_teams.txt") -> "Teo"

A text report counts words longer than three letters.

Specification: Define long_word_count(lines, path). Save each line, then loop through the saved file. For each line.split(), count words whose length is greater than 3. Return the count. Use ex11_words.txt.

Worked sample calls:

long_word_count(["red sails drift", "past docks"], "ex11_words.txt") -> 4

A sign maker wants the longest complete line from a saved list.

Specification: Define longest_line(lines, path) for a nonempty list. Save each line, then reload and strip each line. Track the best text and update it only with strict > length, so a tie keeps the first longest line. Return that text. Use ex12_longest.txt.

Worked sample calls:

longest_line(["ash", "fir hollow", "oak"], "ex12_longest.txt") -> "fir hollow"

A recipe display adds line numbers after loading saved steps.

Specification: Define numbered(lines, path). Save each line, then reload the file. Start number = 1; for each stripped line append f"{number}: {text}" to a rows list and increase the number. Return "\n".join(rows) without a trailing newline. Use ex13_numbered.txt.

Worked sample calls:

numbered(["whisk batter", "add eggs", "bake"], "ex13_numbered.txt") -> "1: whisk batter\n2: add eggs\n3: bake"

A score report needs an average calculated from saved numbers.

Specification: Define saved_average(scores, path) for a nonempty list. Save the scores, then reload each line as an integer. Keep a running total and count, and return total / count. In the stand-in and real program print f"Average: {average}". Use ex14_average.txt.

Worked sample calls:

saved_average([70, 80, 96], "ex14_average.txt") -> 82.0; printed: Average: 82.0

A class report counts scores in four bands.

Specification: Define grade_report(scores, path). Save the scores and reload each as an integer. Start four counters at zero. While reading, use one if/elif/elif/else chain: A for at least 90, B for at least 80, C for at least 70, and D otherwise. Return four f-string rows joined with "\n", labeled A:, B:, C:, D:. Use ex15_grades.txt.

Worked sample calls:

grade_report([91, 78, 85, 62, 97], "ex15_grades.txt") -> "A: 2\nB: 1\nC: 1\nD: 1"

A second file holds an uppercase copy of saved announcements.

Specification: Define shout_copy(lines, source, target). Write the lines to source with "w". Read source line by line and write each .upper() line to target with "w". You may open the target file inside the source file's with block, or first read the lines into a list and then write them. Reload target, strip each line, and return the list. Use ex16_source.txt and ex16_target.txt.

Worked sample calls:

shout_copy(["hush now", "well done"], "ex16_source.txt", "ex16_target.txt") -> ['HUSH NOW', 'WELL DONE']

Only unfinished lines should reach a second file.

Specification: Define keep_todo(lines, source, target). Save lines to source. While reading it, write only lines whose stripped text startswith("TODO") to target. Reload target, strip its lines, and return the list. Use ex17_source.txt and ex17_target.txt.

Worked sample calls:

keep_todo(["TODO paint", "done sweep", "TODO wash"], "ex17_source.txt", "ex17_target.txt") -> ['TODO paint', 'TODO wash']

An event logger keeps a header and appends events as they arrive.

Specification: Define log_events(events, path). Write LOG and a newline with "w". For each event, use its own with open(path, "a") block to append the event and newline. Reload all lines with strip() and return the list. Use ex18_log.txt.

Worked sample calls:

log_events(["start", "jump", "land"], "ex18_log.txt") -> ['LOG', 'start', 'jump', 'land']

A search stops at the first saved word that reaches a minimum length.

Specification: Define first_long_word(words, minimum, path). Save one word per line. While reading, return the first stripped word with len(word) >= minimum. Return "none" only after the loop finishes. Use ex19_first.txt.

Worked sample calls:

first_long_word(["sky", "meadow", "brook"], 5, "ex19_first.txt") -> "meadow"

A roster search needs the line number of its first match.

Specification: Define line_of(names, target, path). Save one name per line. While reloading, start a line counter at 0 and increase it for each line. Return the line number immediately for the first exact match; return -1 after the loop if none matches. Use ex20_names.txt.

Worked sample calls:

line_of(["Rae", "Tovi", "Wen"], "Wen", "ex20_names.txt") -> 3
line_of(["Rae", "Tovi", "Wen"], "Zia", "ex20_names.txt") -> -1

A saved number list becomes a small text chart.

Specification: Define chart_from_file(values, path). Save one number per line. Reload each as an integer, append "#" * number to a rows list, and return "\n".join(rows) with no trailing spaces. Use ex21_chart.txt.

Worked sample calls:

chart_from_file([3, 1, 4], "ex21_chart.txt") -> "###\n#\n####"

A reader opens a file that its program has never created.

Specification: Read the broken code and exact error below. Define read_saved_twelve(path) that first writes 12 and a newline to path with "w", then opens it with "r" and returns the stripped text. The repaired call prints 12. Use ex22_scores.txt for your function.

with open("missing_scores.txt", "r") as f:
    print(f.read())

FileNotFoundError: [Errno 2] No such file or directory: 'missing_scores.txt'

Worked sample calls:

read_saved_twelve("ex22_scores.txt") -> "12"; printed: 12

A saved file exists, but the next operation opens it for reading before trying to write.

Specification: Read the broken code and exact error below. Define write_five(path) that writes 5 and a newline with "w", then reads it back with "r" and returns the stripped text. The repaired call prints 5. Use ex23_mode.txt.

with open("ex_mode.txt", "w") as f:
    f.write("0\n")
with open("ex_mode.txt", "r") as f:
    f.write("5\n")

io.UnsupportedOperation: not writable

Worked sample calls:

write_five("ex23_mode.txt") -> "5"; printed: 5

Two fresh saves and an append are made to the same path.

Specification: Trace the code below before running it. Define predict_overwrite(path) that does the same three writes to its own path and returns the final stripped file text. Explain why the first 1 disappears and the file prints 2 then 3. Use ex24_overwrite.txt.

with open("ex24_overwrite.txt", "w") as f:
    f.write("1\n")
with open("ex24_overwrite.txt", "w") as f:
    f.write("2\n")
with open("ex24_overwrite.txt", "a") as f:
    f.write("3\n")
with open("ex24_overwrite.txt", "r") as f:
    print(f.read().strip())

This code runs without an error. Predict its two printed lines.

Worked sample calls:

predict_overwrite("ex24_overwrite.txt") -> "2\n3"; printed on two lines: 2 / 3

# Define predict_overwrite(path), then try all sample calls.

An arcade manager saves a corrected score list to the same path and wants proof that only the new scores remain.

Specification: Define replace_and_load_scores(first_scores, final_scores, path). First write every value from first_scores to path in "w" mode. After that file closes, open the same path in "w" mode again and write every value from final_scores. Then make an empty list, open the path with with open(path, "r") as f:, transform each line with int(line.strip()), and append it. Return the loaded list, which must contain only the final scores. Use ex25_replace.txt.

Worked sample calls:

replace_and_load_scores([10, 20], [30, 40], "ex25_replace.txt") -> [30, 40]
replace_and_load_scores([99], [4, 5, 6], "ex25_replace.txt") -> [4, 5, 6]
replace_and_load_scores([7, 8, 9], [100], "ex25_replace.txt") -> [100]

A tournament display needs a saved round's total and best score, calculated together while the file is read once.

Specification: Define saved_total_and_best(scores, path). The supplied list always has at least one score. First write every score to path, one per line. Start total = 0 and best = scores[0]. Open the same path with with open(path, "r") as f: and use one for line in f: loop. Convert each line with int(line.strip()), add the score to total, and replace best when the score is greater. Return [total, best]. Do not call sum or max. Use ex26_combined_stats.txt.

Worked sample calls:

saved_total_and_best([12, 30, 18], "ex26_combined_stats.txt") -> [60, 30]
saved_total_and_best([75, 20], "ex26_combined_stats.txt") -> [95, 75]
saved_total_and_best([9], "ex26_combined_stats.txt") -> [9, 9]

Two teams save scores separately and need one ordered result.

Specification: Define merge_files(first, second, path_a, path_b). Save each list to its own file. Reload both files as integers, combine them, call .sort(), and return the ascending list. Use ex27_first.txt and ex27_second.txt.

Worked sample calls:

merge_files([12, 40], [25, 3], "ex27_first.txt", "ex27_second.txt") -> [3, 12, 25, 40]

A new score may change a saved top-three board.

Specification: Define update_high_scores(scores, new_score, path) for at least three starting scores. Save the original scores and reload them as integers. Add new_score, call sorted, and select indexes -1, -2, and -3 in that order. Rewrite path with only those top three scores, reload it, and return the reloaded list. Use ex28_high_scores.txt.

Worked sample calls:

update_high_scores([900, 850, 700], 880, "ex28_high_scores.txt") -> [900, 880, 850]