練習(xí)代碼
from sys import argv
script, filename = argv
print(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("? ")
print("Opening the file...")
target = open(filename, 'w')
print("Truncating the file. Goodbye!")
target.truncate()
print("Now I'm going to ask you for three lines.")
line1 = input("line 1: ")
line2 = input("line 2: ")
line3 = input("line 3: ")
print("I'm going to write these to the file.")
target.write(line1)
target.write("\n")
target.write(line2)
target.write("\n")
target.write(line3)
target.write("\n")
print("And finally, we close it.")
target.close()
Study Drills
If you do not understand this, go back through and use the comment trick to get it squared away in your mind. One simple English comment above each line will help you understand or at least let you know what you need to research more.
Write a script similar to the last exercise that uses read and argv to read the file you just
created.There’s too much repetition in this file. Use strings, formats, and escapes to print out line1,
line2, and line3 with just one target.write() command instead of six.
target.write(line1+"\n"+line2+"\n"+line3+"\n")
- Find out why we had to pass a 'w' as an extra parameter to open. Hint: open tries to be safe by making you explicitly say you want to write a file.
open()方法的默認(rèn)模式是r帝火，也就是只讀模式村生，無(wú)法寫入。
- If you open the file with 'w' mode, then do you really need the target.truncate()? Read
the documentation for Python’s open function and see if that’s true.
不是必需的灶轰。
w模式會(huì)在寫入前自動(dòng)truncate
詳見(jiàn) 官方文檔
補(bǔ)充
-
open的常用模式
chrome_rMhjam4m4c.png
