Read

f = open('starters.csv')
text = f.read()
f.close() # Withouth the f.close, we do not go back to the beggining of the file, as it was already readen
f = open('starters.csv')
surprise = f.readlines()
for i in range(len(surprise)):
    surprise[i] = surprise[i].strip("\n")
print(surprise)

Write

f1 = open("anything.txt", "w")
f1.write("One line\nTwo line")
f1.close()

f2 = open("anything.txt", "a")
f2.write("\nThird Line")
f2.close()

CSV

def printMathematicians():
    data = open("scientists.csv")
    for e in data.readlines():
        for f in e.split(","):
            if f.strip("\n") == "Maths":
                print(e, end="")
    data.close()

def niceScientists(scientists_csv = "scientists.csv"):
    data   = open(scientists_csv)
    output = open("nice-scientists.csv", "w")
    for e in data.readlines():
        if e.split(",")[-1].strip("\n") != "Physics":
            output.write(e)
    data.close()
    output.close()

def mergeScientists():
    data   = open("scientists.csv")
    new    = open("computer-scientists.csv")
    output = open("all-scientists.csv", "w")

    for e in data.readlines():
        output.write(e)

    lines = new.readlines()
    for i in range(1, len(lines)):
        output.write(lines[i].strip("\n") + ",Computer\n")

    data.close()
    new.close()
    output.close()

niceScientists("all-scientists.csv")

Bottles

def greenBottles(n:int) -> bool:
    file = open(f"{n}-green-bottles.txt", "w")
    for i in range(n, 1, -1):
        file.write(f"{i} green bottles hanging on the wall\n{i} green bottles hanging on the wall\nAnd if one green bottle should accidentally fall\nThere'll be {i - 1} green bottles\n")
    file.write(f"1 green bottles hanging on the wall\n1 green bottles hanging on the wall\nAnd if one green bottle should accidentally fall\nThere'll be no green bottles hanging on the wall\n")
    return True