How to wait for the execution of a python script inside shell script?

Question

I want to mount another root partition, edit the grub.cfg file with a python script and afterwards umount the partition again. How can I wait for the python script to finish and check if the partition is ready to be umounted? Currently I have tried to use wait but this doesn't do the trick.

if mountpoint $MPOINT; then
    echo "Already mounted. To prevent potential file loss aborting."
else
    echo "OK, will now mount the needed device."
    mkdir $MPOINT
    mount $DEVICE $MPOINT
    if [ $? -eq 0 ]; then
        # Edit config file
        python /usr/bin/grubcfgmgr.py "$MPOINT" &
        pid=$!
    else
        echo "Failed, could not mount. Aborting."
        rm -rf $MPOINT
        exit n
    fi

    # Umount
    wait $pid
    umount $MPOINT
    if [ $? -eq 0 ]; then
        echo "OK, umount was succesfull. Will delete empty mount point."
        rm -rf $MPOINT
    else
        echo "Failed, could not umount. Aborting."
    fi
fi