Python小程序之sed命令替换

需求：

　　编写sed命令脚本

代码如下

 # Author:Lee Sir

 import sys,os

 des_file = r'E:\StartPython\day3\test.txt'
 des_file1 = r'E:\StartPython\day3\test1.txt'

 parameter = ['','Somehow','',des_file]

 def usage(parameter):
     if len(parameter) == 4:
         if isinstance(parameter[1],str) and isinstance(parameter[2],str):
             old_str = parameter[1]
             new_str = parameter[2]
             if os.path.exists(parameter[3]):
                 des_file = parameter[3]
                 return True, old_str, new_str, des_file
     return False

 def check_string_exist(old,file):
     with open(file,encoding='utf-8') as fd:
         for line in fd:
             if old not in line:
                 return False
             else:
                 return True

 def replace(old,new,file):
     with open(file,'r+',encoding='utf-8') as fd,open(des_file1,'w+',encoding='utf-8') as fd1:
         for line in fd:
             if old in line:
                 new_line = line.replace(old,new)
             else:
                 new_line = line
             print(new_line)
             fd1.write(new_line)

 def main():
     result = usage(parameter)
     if result:
         if check_string_exist(result[1],result[3]):
             replace(result[1],result[2],result[3])
         else:
             print('the %s is not found in %s ' % (result[1],result[3]))
     else:
         exit('USAGE: %s  old_str  new_str  des_file' % sys.argv[0])

 if __name__ == '__main__':
     main()