将输出重定向到python中的文件

Question

In shell script if we have sth like :

field1 = 22
qry="delete from table_name where id = $field1
echo $qry >> /tmp/query.ksh

Here in the file we have

delete from table_name where id = 22

I want to achieve the same in python

How should I achieve this in python I am doing

fo = open("file","a")
fo.write(qry)

But this is not working.

Please suggest the correct way.

Answer 1

Something like what you already have should work fine.

   field1 = 22
   qry = "delete from table_name where id = {0}\n".format(field1)
   with open('your_file', 'a') as f:
     f.write(qry)

what is specifically not working? where is all your python code? you posted only 2 lines where are you defining qry ?

Answer 2

The code you show is correct assuming you want to append to a file named file .

Note that you should close the files that you open or (on recent Python versions) use with statements. Translating your shell code to Python,

field1 = 22
qry = "delete from table_name where id = {}".format(field1)
with open('/tmp/query.ksh', 'a') as of:
    of.write(qry)

Note that in real life you should not directly insert data into prepared SQL statements, because it can possibly lead to SQL injections.

Answer 3

Your code is working, alternatively you can direct print output to file by doing this:

import sys
sys.stdout = open("file","a")

field1 = 22
qry = "delete from table_name where id = {0}\n".format(field1)
print qry