r模式，只读，不存在该文件时报错
r+模式，读写，不存在该文件时报错,覆盖写
w模式，只写，不存在该文件时创建，会将文件内容清空再写
w+模式，读写，不存在该文件时创建，会将文件内容清空再写
a模式，只写，不存在该文件时创建，附加写
a+模式，读写，不存在该文件时创建，附加写

附上练习代码

from sys import argvscript, filename = argvprint(f"We're going to erase {filename}.")
print("If you don't want that, hit CTRL-C (^C).")
print("If you do want that, hit RETURN.")
input("?")#模式练习
print("Opening the file...")
target = open(filename, 'w')print("Truncating the file. Goodbye!")#清空文件，不写这句也没事，写模式默认会清空的
target.truncate()print("Now I'm going to ask you for three lines.")lines1 = input("line 1: ")
lines2 = input("line 2: ")
lines3 = input("line 3: ")print("I'm going to write these to the file.")target.write(lines1 + "\n" + lines2 + "\n" + lines3 + "\n")print("And finally, we close it.")
target.close()