[Python] Why does Flask + ReportLab lets me only make 1 pdf before I need to restart server?

I am trying to make a small app for making pdfs and all is good until I try to make a second pdf.

Here are the steps to encounter the issue:

• Run flask app
• Go to 127.0.0.1:5000
• Fill in the form fields then submit
• Check generated pdf (it works!)
• Back in the browser so that we see the form and fill it out again
• Submit
• Check generated pdf (it does not work)
• Restart the flask server and try above steps again (it works but again only for the first attempt)

This is the flask app I am using. create.html is just a html form and the data grabbed will be sent to pdfCreater.py to generate the

from flask import Flask, render_template, request, redirect, url_for
import pdfcreater

app = Flask(__name__)

@app.route("/", methods=["POST", "GET"])
def index():
if request.method == 'POST':
keys = request.form.keys()
data = []
temp = []

for key in keys:
temp.append(request.form[key])

for i in range(0, len(temp), 4):
data.append([temp, temp[i+1], temp[i+2], temp[i+3]])
print()
return redirect(url_for("createPdf", formData=data))
else:
return render_template("create.html")

@app.route("/<formData>")
def createPdf(formData):
pdfcreater.main(formData)

return f"<h1>{formData}</h1>"


if __name__ == '__main__':
app.run(debug=True)



Here is pdfCreater.py:

from reportlab.pdfgen import canvas
from reportlab.lib.units import inch, cm
from reportlab.lib.pagesizes import letter
from reportlab.platypus import Spacer, SimpleDocTemplate, Table, TableStyle, Paragraph, paragraph
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle


story = [Spacer(1, 0)]

def main(data):

def my_first_page(canvas, doc):

styles = getSampleStyleSheet()
title_style = ParagraphStyle(
name='TitleStyle',
parent=styles['Title'], # Inherit from the default Title style
fontName='Helvetica-Bold', # Specify the font name
fontSize=24, # Set the font size
leading=28, # Adjust line spacing
alignment=1 # Center the title
)


centered_style = ParagraphStyle(
name='CenteredStyle',
parent=styles['Normal'], # Inherit from the default Normal style
alignment=1, # Align the text to the center
fontSize=14,
leading=16
)


customer_style = ParagraphStyle(
name='CenteredStyle',
parent=styles['Normal'], # Inherit from the default Normal style
alignment=1, # Align the text to the center
fontSize=16,
leading=20
)



left_align = ParagraphStyle(
name='reightAlignedStyle',
parent=styles['Normal'], # Inherit from the default Normal style
alignment=0, # Align the text to the right
fontSize=14,
leading=0
)

right_align = ParagraphStyle(
name='reightAlignedStyle',
parent=styles['Normal'], # Inherit from the default Normal style
alignment=2, # Align the text to the right
fontSize=14,
leading=16
)


sig_style = ParagraphStyle(
name='signature',
parent=styles['Normal'], # Inherit from the default Normal style
alignment=0, # Align the text to the right
fontSize=11,
leading=0
)


styles = getSampleStyleSheet()
blank_line = Paragraph("", title_style)
title = Paragraph("SOMETHING SOMETHING", title_style)
story.append(title)


line_of_text = Paragraph(CONFIDENTIAL", centered_style)
story.append(line_of_text)
story.append(blank_line)


date_invoice = "Date: 22/12/00"
iNum = 12345
invoice_num = f"Invoice: {iNum}"
l1 = Paragraph(date_invoice, left_align)
l2 = Paragraph(invoice_num, right_align)
story.append(l1)
story.append(l2)


customer = "customeeeeeeeeeeeeeeeeeeeeeeeeeer"
l3 = Paragraph(customer, customer_style)
story.append(l3)



invoice_data = [["gdata", "a", "b", "c"]]
invoice_data = [
['Item', 'Description', 'Description', 'Price'],
['Item 2', 'Description 2', 'Description 1', 'Price']
]
print("=================", data[0])
for item in data:
invoice_data.append(item)

while len(invoice_data) < 21:
invoice_data.append([])
# ... other items


styles = getSampleStyleSheet()
table = Table(invoice_data, colWidths=[1.25 * cm, 12.25 * cm, 2.5 *cm, 3 * cm])


n = -1
# Apply table styles (customize as needed)
table.setStyle(TableStyle([
('ALIGN', (1, 1), (-1, -1), 'LEFT'),
('TEXTCOLOR', (0, 0), (-1, 0), 'grey'),
('SPAN', (0, n), (2, n)),
('VALIGN', (0, 0), (-1, -1), 'MIDDLE'),
('INNERGRID', (0, 0), (-1, -1), 0.25, 'black'),
('BOX', (0, 0), (-1, -1), 0.25, 'black'),
]))


story.append(table)

for i in range(6):
story.append(blank_line)
sig = Paragraph("_"*24, left_align)
story.append(sig)
story.append(blank_line)
story.append(blank_line)
story.append(blank_line)
story.append(Paragraph('Signature of customer/receiving officer', sig_style))

story.append(blank_line)
story.append(blank_line)
story.append(blank_line)
story.append(blank_line)
story.append(blank_line)

story.append(sig)
story.append(blank_line)
story.append(blank_line)
story.append(blank_line)
story.append(Spacer(5 * cm, 0))
story.append(Paragraph('Name of customer/receiving officer', sig_style))
try:
print("-----------",type(eval(data)) == type([]))

if type(eval(data)) == type([]):

data = eval(data)

# fetch_data(data)
doc = SimpleDocTemplate("invoice.pdf", pagesize=letter)
# Assuming 'taaable' is your table object

doc.build(story, onFirstPage=my_first_page, onLaterPages=my_first_page)

except:
pass


Any idea why this happens? Thanks in advance!

After searching the internet I tried caching as well as trying to identify bottlenecks in the code but couldn't find anything.

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