在python中使用「w」模式有什麼意義？

Question

#From the sys package, i'm importing the argv 
from sys import argv 
#Un packaging the arguments 
script, filename = argv 
#Print statements 
print "We're going to erase %r." % filename 
print "If you don't want that, hit CTRL-C (^C)." 
print "If you do want that, hit RETURN." 
#To accept whether or not we want to continue or not 
raw_input("?") 

print "Opening the file..." 
# I am opening the file 
target = open(filename) 

print "Truncating the file. Goodbye!" 
target.truncate() 

print "Now i'm going to ask you for three lines." 

line1 = raw_input("line 1: ") 
line2 = raw_input("line 2: ") 
line3 = raw_input("line 3: ") 

print "I'm going to write these to the file." 
x = "%r\n %r\n %r\n" % (line1, line2, line3) 
target.write(x) 
#This also works to write the files 
# target.write ("%r\n%r\n%r\n" % (line1, line2, line3)) 

print "And finally, we close it." 
target.close() 

對於open(filename)，我覺得我得到了相同的結果，當我把劇本在行動open(filename "w")

什麼是「W」，然後點？由於我已經有了一個函數來寫入target.write（）命令！

Answer 1

根據​​：

的模式最常用的值是「R」讀，寫（截斷如果它已經存在的文件），「W」和「A」的追加（在某些Unix系統上，這意味着無論當前的查找位置如何，所有寫操作都會追加到文件末尾）。如果省略模式，則默認爲'r'。

Answer 2

「w」模式創建文件，如果它不存在，並清空它，如果它。