Python and Bash slow print function

I always liked to toy with slow printing terminal functions that have a small delay between each character (a bit Matrix style). Here is the Python 3 version:

Syntax highlighted version here.

#! /usr/bin/env python3

import os, sys, time

def dprint (message, delay=0.1):
        """
        Prints message with delay between each character.
        """
        for char in message:
                sys.stdout.write(char)
                sys.stdout.flush()
                time.sleep(delay)

if __name__ == '__main__':
        """
        Demonstration logic.
        """
        os.system('clear')
        dprint('This message is printed slowly and demonstrates the slow\n' +
               'print function.')

Below is an older version written as a bash shell script which does the same.

Syntax highlighted version here.

#! /bin/bash

mm_decho ()
{
        local i stepping
        stepping="0.01"

        # When first argument is empty or not given, it just echoes a new line
        # and leaves.
        if [ ! "$1" ]; then 
                echo
                return
        fi

        # If a second argument is given (delay stepping), check it for validity
        # (if it is a float) and set stepping according to the argument.
        if  (( $# > 1 )) && 
            [[ ($2 = $(echo $2 | grep -oE '[[:digit:]]')) ||
               ($2 = $(echo $2 | grep -oE '[[:digit:]]+\.[[:digit:]]+')) ]] 
            then
                stepping="$2"
        # In case the previous test failed, but we have a second argument,
        # meaning it is invalid, just print the message, complain a bit and then
        # quit the function with false.
        elif (( $# > 1 )); then
                echo "$1"
                echo ".! mm_decho() oops: second argument is invalid!" 1>&2
                echo ".! must be /float but is: \"$2\", leaving function.." 1>&2
                return false 2>/dev/null
        fi

        # Do delayed printing of first input argument. Calculate the
        # length of first arg. and substract one. Then make it a /for/
        # sequence going through all the characters of the string,
        # printing these and wait the delay stepping time.
        for i in $(seq 0 $((${#1}-1))); do
                echo -n "${1:$i:1}"
                sleep $stepping
        done
        echo
}


mm_decho "Should be ok, default.."
mm_decho "Should be ok, costume stepping.." "0.05" "some more arg"
mm_decho "Should be ok, costume stepping.." "0.05"
mm_decho "" "0.3"