Reportlab: Pass custom argument to Canvas - python-3.x

Question

I'm working on a report generator with Python. So far everything is going well, except for a single detail: I need to add a custom footer to the report. Since I'm also addingg more elements, I need to use a custom Canvas object to build the report, and I think it should be possible to add this custom footer to the canvas class... but so far I've had no success.
Here's the code I've been writing:
Imports:
from reportlab.pdfgen import canvas
from reportlab.platypus import SimpleDocTemplate, Paragraph
from reportlab.lib.units import cm
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.pagesizes import letter
from reportlab.lib.enums import TA_JUSTIFY
Custom Canvas class:
class CustomCanvas(canvas.Canvas):
"""
Adapted from http://code.activestate.com/recipes/576832/
"""
def __init__(self, *args, **kwargs):
canvas.Canvas.__init__(self, *args, **kwargs)
self._saved_page_states = []
# I'd like to pass the custom footer text to the constructor
# to draw it at the footer for each page. This is a fragment of
# text that will be read from a database
if 'customFooterText' in kwargs:
self.customFooter = kwargs['customFooterText']
else:
self.customFooter = 'Missing custom footer text :('
def showPage(self):
self._saved_page_states.append(dict(self.__dict__))
self._startPage()
def drawPageNumber(self, page_count):
self.setFont('Helvetica', 8)
self.drawRightString(21 * cm, 1 * cm,
'%s / %s' % (self._pageNumber, page_count))
def drawCustomFooter(self):
"""
Here is where I'd like to draw the custom footer.
"""
self.setFont('Helvetica', 8)
self.drawString(1 * cm, 1 * cm, self.customFooter)
def save(self):
num_pages = len(self._saved_page_states)
for state in self._saved_page_states:
self.__dict__.update(state)
self.drawPageNumber(num_pages)
self.drawCustomFooter()
canvas.Canvas.showPage(self)
canvas.Canvas.save(self)
My Report builder:
class MyReport:
def __init__(self):
self.filename = 'test.pdf'
self.doc = SimpleDocTemplate(self.filename, pagesize=letter,
topMargin = 1 * cm, bottomMargin = 2 * cm,
leftMargin = 1 * cm, rightMargin = 1 * cm)
self.Story = []
def generateReport(self):
self.reportContent()
self.doc.build(self.Story, canvasmaker=CustomCanvas)
# Here is the issue: How to pass the kwarg to the CustomCanvas
# class so it can be drawn in each page?
def reportContent(self):
# In the "real life", this content will be generated with data from
# a database.
styles = getSampleStyleSheet()
styles.add(ParagraphStyle(name='Justify', alignment=TA_JUSTIFY))
justify = styles['Justify']
txt = """
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Maecenas tristique cursus enim at luctus. Proin tincidunt,
arcu vitae mattis pretium, lorem eros semper lectus,
venenatis luctus orci odio rhoncus nunc. Nam nulla arcu,
hendrerit at lacinia eget, gravida aliquam quam. Mauris
finibus ipsum at leo ullamcorper, ut faucibus est eleifend.
Maecenas vehicula malesuada tempor. Nulla et augue a purus
luctus tincidunt. Nam consectetur ut diam sit amet efficitur.
Morbi a volutpat orci. Donec id ipsum ut quam hendrerit gravida.
Nulla gravida, ante non euismod fermentum, metus nulla ullamcorper
sem, ut feugiat ipsum felis sit amet lectus.
"""
for i in range(15):
self.Story.append(Paragraph(txt, justify))
Test
report = MyReport()
report.generateReport()
When creating the report, the first page looks something like this:
So, the question is: How to add that string to each page using a kwarg in the CustomCanvas class?

Answer 1

I found a way to do what I need... I left alone the custom canvas and used the onFirstPage and onLaterPages parameters to include my custom footer (I don't care where the custom footer string is specified, as long as I can specify it at runtime).
My solution:
Imports:
from reportlab.pdfgen import canvas
from reportlab.platypus import SimpleDocTemplate, Paragraph
from reportlab.lib.units import cm
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.pagesizes import letter
from reportlab.lib.enums import TA_JUSTIFY
Custom Canvas class:
I left alone the Custom Canvas class. It does what it needs to do:
class CustomCanvas(canvas.Canvas):
"""
Adapted from http://code.activestate.com/recipes/576832/
"""
def __init__(self, *args, **kwargs):
canvas.Canvas.__init__(self, *args, **kwargs)
self._saved_page_states = []
def showPage(self):
self._saved_page_states.append(dict(self.__dict__))
self._startPage()
def drawPageNumber(self, page_count):
self.setFont('Helvetica', 8)
self.drawRightString(21 * cm, 1 * cm,
'%s / %s' % (self._pageNumber, page_count))
def save(self):
num_pages = len(self._saved_page_states)
for state in self._saved_page_states:
self.__dict__.update(state)
self.drawPageNumber(num_pages)
canvas.Canvas.showPage(self)
canvas.Canvas.save(self)
My Report builder:
Here I added my **kwargs parameter, so I can pass a custom argument with the footer text:
class MyReport:
def __init__(self, *args, **kwargs):
self.filename = 'test.pdf'
self.doc = SimpleDocTemplate(self.filename, pagesize=letter,
topMargin = 1 * cm, bottomMargin = 2 * cm,
leftMargin = 1 * cm, rightMargin = 1 * cm)
if 'left_footer' in kwargs:
self.left_footer = kwargs['left_footer']
else:
self.left_footer = None
self.Story = []
def onMyFirstPage(self, canvas, doc):
# If the left_footer attribute is not None, then add it to the page
canvas.saveState()
if self.left_footer is not None:
canvas.setFont('Helvetica', 8)
canvas.drawString(1 * cm, 1 * cm, self.left_footer)
canvas.restoreState()
def onMyLaterPages(self, canvas, doc):
# If the left_footer attribute is not None, then add it to the page
canvas.saveState()
if self.left_footer is not None:
canvas.setFont('Helvetica', 8)
canvas.drawString(1 * cm, 1 * cm, self.left_footer)
canvas.restoreState()
def generateReport(self):
self.reportContent()
self.doc.build(self.Story, canvasmaker=CustomCanvas,
onFirstPage=self.onMyFirstPage,
onLaterPages=self.onMyLaterPages)
def reportContent(self):
styles = getSampleStyleSheet()
styles.add(ParagraphStyle(name='Justify', alignment=TA_JUSTIFY))
justify = styles['Justify']
txt = """
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Maecenas tristique cursus enim at luctus. Proin tincidunt,
arcu vitae mattis pretium, lorem eros semper lectus,
venenatis luctus orci odio rhoncus nunc. Nam nulla arcu,
hendrerit at lacinia eget, gravida aliquam quam. Mauris
finibus ipsum at leo ullamcorper, ut faucibus est eleifend.
Maecenas vehicula malesuada tempor. Nulla et augue a purus
luctus tincidunt. Nam consectetur ut diam sit amet efficitur.
Morbi a volutpat orci. Donec id ipsum ut quam hendrerit gravida.
Nulla gravida, ante non euismod fermentum, metus nulla ullamcorper
sem, ut feugiat ipsum felis sit amet lectus.
"""
for i in range(15):
self.Story.append(Paragraph(txt, justify))
Test
report = MyReport(left_footer='A custom test footer for my pages')
# I can now specify my custom footer in runtime!
report.generateReport()
I feel kinda dumb now that I've found that it was so easy.
But I leave this to posterity, in case someone needs to do something similar.
Anyway, if anybody else has a better solution, please add your answer.