文件读取和写入的问题

Question

from os import strerror

srcname = input("Enter the source file name: ")
try:
    src = open(srcname, 'rb')
except IOError as e:
    print("Cannot open the source file: ", strerror(e.errno))
    exit(e.errno)    

dstname = input("Enter the destination file name: ")
try:
    dst = open(dstname, 'wb')
except Exception as e:
    print("Cannot create the destination file: ", strerror(e.errno))
    src.close()
    exit(e.errno)    

buffer = bytearray(65536)
total  = 0
try:
    readin = src.readinto(buffer)
    print(readin)
    while readin > 0:
        written = dst.write(buffer[:readin])
        print(written)
        total += written
        readin = src.readinto(buffer)
        print(readin)
except IOError as e:
    print("Cannot create the destination file: ", strerror(e.errno))
    exit(e.errno)    
    
print(total,'byte(s) succesfully written')
src.close()
dst.close()

#written = dst.write(buffer[:readin])如何认定这就是读取的文件

Answer 1

因为你是通过src.readin(buffer)读取的，将内容读取到buffer中。
然后写入dst中，操作的是butter。

#读取src文件中的内容，将内容存储buffer变量中
    readin = src.readinto(buffer)
    #输出当前读取内容的有效长度
    print(readin)
    #如果当前有效长度大于0，说明文件中存在内容，循环遍历读取
    while readin > 0:
        #边读边写
        #将buffer中的内容写入dst文件对象中
        written = dst.write(buffer[:readin])
        #打印当前写入的内容长度
        print(written)
        #统计所有写入文件中的内容长度
        total += written
        #继续读取
        readin = src.readinto(buffer)
        print(readin)