Add line on top of each Python file in current and sub directories

Question

I'm on an Ubuntu platform and have a directory containing many .py files and subdirectories (also containing .py files). I would like to add a line of text to the top of each .py file. What's the easiest way to do that using Perl, Python, or shell script?

Answer 1

find . -name \*.py | xargs sed -i '1a Line of text here'

Edit: from tchrist's comment, handle filenames with spaces.

Assuming you have GNU find and xargs (as you specified the linux tag on the question)

find . -name \*.py -print0 | xargs -0 sed -i '1a Line of text here'

Without GNU tools, you'd do something like:

while IFS= read -r filename; do
  { echo "new line"; cat "$filename"; } > tmpfile && mv tmpfile "$filename"
done < <(find . -name \*.py -print)

Answer 2

for a in `find . -name '*.py'` ; do cp "$a" "$a.cp" ; echo "Added line" > "$a" ; cat "$a.cp" >> "$a" ; rm "$a.cp" ; done

Answer 3

    #!/usr/bin/perl

    use Tie::File;
    for (@ARGV) {
        tie my @array, 'Tie::File', $_ or die $!; 
        unshift @array, "A new line";        
    }

To process all .py files in a directory recursively run this command in your shell:

find . -name '*.py' | xargs perl script.pl