【Python求教】这段代码不知道哪里错了。

Question

from sys import argv
from os.path import exists

script, from_file, to_file = argv

print "We will copy %s to %s." % (from_file, to_file)

indata = open(from_file).read()

print "The input file is %d bytes long." % len(indata)

print "Does the output file exist? %r" % exists(to_file)
print "Ready, hit enter to continue, CTRL-C to abort."
raw_input()

txt = open(to_file, 'w').write(indata)

print txt.read()

一直显示
AttributeError：'Nonetype'object has no attribute 'read'.

Answer 1

    txt = open(to_file, 'w').write(indata)

这段代码执行完后，txt并不是file对象，而是write(indata)函数所返回的对象，根据python文档

此函数返回None，所以会产生上述错误。