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# ex15
# 打开文件并读取文件内容
from sys import argv
script, filename = argv
txt = open(filename) # 根据文件名打开文件
print(f"Here's your file {filename}:")
print(txt.read()) # 读取该文件中的文本并输出
print("Type the filename again:")
file_again = input("> ")
txt_again = open(file_again)
print(txt_again.read())
# ex16
# 文件的写入
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).") # 输出CTRL-C指令，可中断执行
print("If you do want that, hit RETURN.")
input("?")
print("Opening the file...")
target = open(filename, 'w') # 以write的模式打开文件
print("Truncating the file. Goodbye!")
target.truncate() # 此步非必须，若无此函数，以w模式打开文件，则系统首先会自动将文件清空
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.")
# 第一种写入三行文字的方式
target.write(line1)
target.write("\n")
target.write(line2)
target.write("\n")
target.write(line3)
target.write("\n")
# 以string的方式写入三行文字
#target.write(line1 + "\n" + line2 + "\n" + line3 + "\n")
# 以format的方式写入三行文字
# 其一
#target.write(f"{line1}\n{line2}\n{line3}\n")
# 其二
#formatter = "{}\n{}\n{}\n"
#target.write(formatter.format(line1, line2, line3))
print("And finally, we close it.")
target.close()
# ex17
# 文件的拷贝
from sys import argv
from os.path import exists
script, from_file, to_file = argv
print(f"Copying from {from_file} to {to_file}")
in_file = open(from_file)
indata = in_file.read()
print(f"The input file is {len(indata)} bytes long") # len(indata)获取indata的长度
print(f"Dose the output file exist? {exists(to_file)}") # exists(to_file)检测文件是否存在，存在返回True
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()
# 用一行来实现上述功能，即文件的copy（此时打开的两个文件是否会被python自动关闭？）
# open(to_file,'w').write(open(from_file).read())