自定义replace函数，模仿shell的sed替换

 

import sys
"""
Usages:
    1.  command line:  python replacestr.py para1 para2 para3;
    2.  para1 : file_name
        para2 : original string
        para3 : new string 
"""

file_name = sys.argv[1]
find_str = sys.argv[2]
replace_str = sys.argv[3]

f=""
with open(file_name, "r") as fs1:
    for n in fs1:
        f += n.replace(find_str, replace_str)
  
with open(file_name, "w") as fs2:
    fs2.write(f)
    fs2.flush()