with open("flights.txt", "w") as f:
    f.write("name,altitude_km,duration_min\n")
    f.write("Mercury-Redstone 3,187,15\n")
    f.write("Vostok 1,327,108\n")

with open("flights.txt", "r") as f:
    contents = f.read()

print(contents)
print(type(contents))

name,altitude_km,duration_min
Mercury-Redstone 3,187,15
Vostok 1,327,108

<class 'str'>