文件操作练习题

#想要读取一个文件的第三行

fp = open("e:\a.txt","r",encoding="utf-8")

n=1

for  line in fp:  #fp是句柄，为可迭代对象，所以能用for循环

    if n==3:

        print(line)

    n+=1

fp.close()

 

 

升级小练习：请把它封装到一个函数里面

import os.path

 

 

def read_specific_line(file_path,line_number,encoding="utf-8"):

    if not os.path.exists(file_path):

        return None

    if not isinstance(line_number,int):

        return None

    content  = None

    fp = open(file_path,"r",encoding=encoding)

    n=1

    for line in fp:

        if n==line_number:

            content = line

        n+=1

    fp.close()

    return content

 

 

print(read_specific_line("e:\a.txt",3,"utf-8"))

 

 

#健壮版：如果编码格式不对，用try...except...

import os.path

def read_specific_line(file_path,line_number,encoding="utf-8"):
    if not os.path.exists(file_path):
        return None
    if not isinstance(line_number,int):
        return None

    content  = None
    try:
        fp = open(file_path,"r",encoding=encoding)
        n=1
        for line in fp:
            if n==line_number:
                content = line
                fp.close()
                return content
            n+=1
        fp.close()     
    except:
        print("编码设定错误，请更换编码参数重试！")
        return content

print(read_specific_line("e:\a.txt",3,"utf-8"))