To grep on the results of a find command, you can use something like

find . -iname '*.py' -exec grep something -inH --color {} +

Another solution is to use xargs

find . -iname '*.py' -print0 | xargs -0 grep something -inH --color

The output can be redirected to a file

find . -iname '*.py' -exec grep something -inH --color {} + > output.txt

Notes:

Here is an excerpt from the man page of find (https://man7.org/linux/man-pages/man1/find.1.html → search for “-exec command {} +”)

       -exec command {} +
              This variant of the -exec action runs the specified
              command on the selected files, but the command line is
              built by appending each selected file name at the end; the
              total number of invocations of the command will be much
              less than the number of matched files.  The command line
              is built in much the same way that xargs builds its
              command lines.  Only one instance of `{}' is allowed
              within the command, and it must appear at the end,
              immediately before the `+'; it needs to be escaped (with a
              `\') or quoted to protect it from interpretation by the
              shell.  The command is executed in the starting directory.
              If any invocation with the `+' form returns a non-zero
              value as exit status, then find returns a non-zero exit
              status.  If find encounters an error, this can sometimes
              cause an immediate exit, so some pending commands may not
              be run at all.  For this reason -exec my-
              command ... {} + -quit may not result in my-command
              actually being run.  This variant of -exec always returns
              true.