合并文件内容到另一个文件尾部[python]

#!/usr/bin/python
#coding:utf-8
"""
"""
import sys,os
from contextlib import nested

def MergeEnvFile(newfile,oldfile):
    with nested(open(newfile,'a'), open(oldfile, 'r')) as (new_file, old_file) :
        old_file_lines = old_file.readlines();
        new_file.write('\n');
        new_file.write("  env:");
        new_file.write('\n');
        for line in old_file_lines:
            new_line = line.strip().replace("=",": ",1);
            #Process the second half of the string.
            line_key = new_line.strip().split(":",1)[0];
            line_value = new_line.strip().split(":",1)[1];
            new_line = line_key+": "+'"'+line_value.strip()+'"';
            ###############################
            new_file.write('    '+new_line);
            new_file.write("\n");
        new_file.close();

if  __name__ == "__main__" :
    MergeEnvFile('temp.yaml','env');