Try unicode:
up_arrow = '\u2197' # Up arrow
down_arrow = '\u2198' # Down arrow
right_arrow = '\u2192' # Right arrow
Comment out (or delete) the following:
#Set font properties for the first three rows
#for (i, j), cell in rect.get_celld().items():
# if i < 3: # First three rows
# cell.set_fontsize(12)
# cell.set_text_props(fontname='Arial') # Change to your desired fon t
# else: # Last row with Wingdings
# cell.set_fontsize(12)
# cell.set_text_props(fontname='Wingdings 3')
The output: