python中的函数调用

def file_view(file_name,line_num):
   number = line_num.split(':')
   count=0
   with open(file_name,encoding='utf-8') as f1:
       count=len(f1.readlines())
   f = open(file_name,encoding='utf-8')
   if number[0]=='' and number[1]=='':
       print('\n%s文件全文的内容如下：\n'%(file_name))
       for i in range(count):
           print(f.readline(),end='')
   elif number[0]=='' and number[1]!='':
       print('\n文件%s从开始到%s行的内容如下：\n'%(file_name,number[1]))
       for i in range(int(number[1])):
           print(f.readline(),end='')
       f.close()
   elif number[0]!='' and number[1]=='':
       print('\n文件%s从%s行到末尾的内容如下：\n'%(file_name,number[0]))
       for i in range(count):
           if i >= int(number[0])-1:
               print(f.readline(),end='')
           else:
               f.readline()
       f.close()
   else:
       print('\n文件%s从%s行到%s行的内容如下：\n'%(file_name,number[0],number[1]))
       for i in range(count):
           if i >= int(number[0])-1 and i<= int(number[1])-1:
               print(f.readline(),end='')
       f.close()
file_name = input(r'请输入要打开的文件（C:\\test.txt）:')
line_num = input('请输入需要显示的行数【格式如13:21或:21或21:】：')
file_view(file_name,line_num)

逻辑上不是太完美， 但也正常工作了。

def file_view(file_name, line_num):
    number = line_num.split(':')
    count = 0
    with open(file_name, encoding='utf-8') as f1:
        count = len(f1.readlines())
    f = open(file_name, encoding='utf-8')
    if number[0] == '' and number[1] == '':
        print('\n%s文件全文的内容如下：\n' % (file_name))
        for i in range(count):
            print(f.readline(), end='')
    elif number[0] == '' and number[1] != '':
        print('\n文件%s从开始到%s行的内容如下：\n' % (file_name, number[1]))
        for i in range(int(number[1])):
            print(f.readline(), end='')
        f.close()
    elif number[0] != '' and number[1] == '':
        print('\n文件%s从%s行到末尾的内容如下：\n' % (file_name, number[0]))
        for i in range(count):
            line_str = f.readline()
            # print(i,line_str)
            if i >= (int(number[0]) - 1):
                print(line_str, end='')

        f.close()
    else:
        print('\n文件%s从%s行到%s行的内容如下：\n' % (file_name, number[0], number[1]))
        for i in range(count):
            line_str = f.readline()
            if i >= int(number[0]) - 1 and i <= int(number[1]) - 1:
                print(line_str, end='')
        f.close()


file_name = input(r'请输入要打开的文件（C:\\test.txt）:')
line_num = input('请输入需要显示的行数【格式如13:21或:21或21:】：')
file_view(file_name, line_num)