Why is an MD5 hash created by Python different from one created using echo and md5sum in the shell?
echo appends a \n since you usually do not want lines not ending with a linebreak in your shell (it looks really ugly if the prompt does not start at the very left).
Use the -n argument to omit the trailing linebreak and it will print the same checksum as your python script:
> echo -n mystringforhash | md5sum86b6423cb6d211734fc7d81bbc5e11d3 -