《笨办法学python3-Learn Python 3 the HARD WAY》-习题17 更多文件操作

学习内容：

from sys import argv
from os.path import exists

script, from_file, to_file = argv

print (f"Copying from {from_file} to {to_file}")

# we could do these two on one line, how?
in_file = open(from_file)
indata = in_file.read()

print (f"The input file is {len(indata)} bytes long")

print (f"Does the output file exist? {exists(to_file)}")
print ("Ready, hit RETURN to continue,CTRL-C to abort.")
input()

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

print ("Alright, all done.")

out_file.close()
in_file.close()

运行结果：
选择RETURN运行结果如下：
txteg.txt文件的内容已复制到txtc.txt中：

选择CTRL-C运行结果如下：

知识点：

1. 简化脚本

from sys import argv

script, from_file = argv

old_file = open(from_file)
document = old_file.read()

new_file = open(input('new '), 'w')
new_file.write(document)

old_file.close()
new_file.close()

运行结果：

2. len()
返回括号内的数量：例如文件内的字符数量。