A class to manage printing on Avery labels with ReportLab

AveryLabels.py

import os
from collections.abc import Iterator
from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import LETTER, landscape
from reportlab.lib.units import inch, mm, cm
from reportlab.pdfbase import pdfmetrics
from reportlab.pdfbase.ttfonts import TTFont

# Usage:
#   label = AveryLabels.AveryLabel(5160)
#   label.open( "labels5160.pdf" )
#   label.render( RenderAddress, 30 )
#   label.close()
#
# 'render' can either pass a callable, which receives the canvas object
# (with X,Y=0,0 at the lower right) or a string "form" name of a form
# previously created with canv.beginForm().


# labels across
# labels down
# label size w/h
# label gutter across/down
# page margins left/top

labelInfo = {
    4731: (7, 27, (25.4*mm, 10*mm), (0.25*cm, 0), (0.85*cm, 1.35*cm) ),
    # 2.6 x 1 address labels
    5160: ( 3, 10, (187,  72), (11, 0), (14, 36)),
    5161: ( 2, 10, (288,  72), (0, 0), (18, 36)),
    # 4 x 2 address labels
    5163: ( 2,  5, (288, 144), (0, 0), (18, 36)),
    # 1.75 x 0.5 return address labels
    5167: ( 4, 20, (126,  36), (0, 0), (54, 36)),
    # 3.5 x 2 business cards
    5371: ( 2,  5, (252, 144), (0, 0), (54, 36)),
}

RETURN_ADDRESS = 5167
BUSINESS_CARDS = 5371

class AveryLabel:

    def __init__(self, label, **kwargs):
        data = labelInfo[label]
        self.across = data[0]
        self.down = data[1]
        self.size = data[2]
        self.labelsep = self.size[0]+data[3][0], self.size[1]+data[3][1]
        self.margins = data[4]
        self.topDown = True
        self.debug = False
        self.pagesize = LETTER
        self.position = 0
        self.__dict__.update(kwargs)

    def open(self, filename):
        self.canvas = canvas.Canvas( filename, pagesize=self.pagesize )
        if self.debug:
            self.canvas.setPageCompression( 0 )
        self.canvas.setLineJoin(1)
        self.canvas.setLineCap(1)

    def topLeft(self, x=None, y=None):
        if x == None:
            x = self.position
        if y == None:
            if self.topDown:
                x,y = divmod(x, self.down)
            else:
                y,x = divmod(x, self.across)

        return (
            self.margins[0]+x*self.labelsep[0],
            self.pagesize[1] - self.margins[1] - (y+1)*self.labelsep[1]
        )

    def advance(self):
        self.position += 1
        if self.position == self.across * self.down:
            self.canvas.showPage()
            self.position = 0

    def close(self):
        if self.position:
            self.canvas.showPage()
        self.canvas.save()
        self.canvas = None

    # To render, you can either create a template and tell me
    # "go draw N of these templates" or provide a callback.
    # Callback receives canvas, width, height.
    #
    # Or, pass a callable and an iterator.  We'll do one label
    # per iteration of the iterator.

    def render( self, thing, count, *args ):
        assert callable(thing) or isinstance(thing, str)
        if isinstance(count, Iterator):
            return self.render_iterator( thing, count )

        canv = self.canvas
        for i in range(count):
            canv.saveState()
            canv.translate( *self.topLeft() )
            if self.debug:
                canv.setLineWidth( 0.25 )
                canv.rect( 0, 0, self.size[0], self.size[1] )
            if callable(thing):
                thing( canv, self.size[0], self.size[1], *args )
            elif isinstance(thing, str):
                canv.doForm(thing)
            canv.restoreState()
            self.advance()

    def render_iterator( self, func, iterator ):
        canv = self.canvas
        for chunk in iterator:
            canv.saveState()
            canv.translate( *self.topLeft() )
            if self.debug:
                canv.setLineWidth( 0.25 )
                canv.rect( 0, 0, self.size[0], self.size[1] )
            func( canv, self.size[0], self.size[1], chunk )
            canv.restoreState()
            self.advance()