如何在python中全局导入？

Question

I was just getting started with reportlab, when I stumbled upon something. I started with some basic code:

from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas

def generateDoc(docName, title, codefilesFolderPath, docTextFilePath):

    canvas = canvas.Canvas(docName, pagesize=letter) 
    canvas.setLineWidth(.3)
    canvas.setFont('Helvetica', 12)
    canvas.drawString(30,750,'OFFICIAL COMMUNIQUE')
    canvas.save()

generateDoc("temp.pdf","","","")

It was giving me following error:

UnboundLocalError: local variable 'canvas' referenced before assignment

I have come to know that global variables are not freely allowed in python as in case of other languages and this post asks to use global keyword. However I am unable to get how I am supposed to do that in above code.

I tried putting import at various places, but I am not able to get how do I do this.

Answer 1

Your local variable canvas hides the imported module canvas .

You could import Canvas directly:

from reportlab.lib.pagesizes import letter
from reportlab.pdfgen.canvas import Canvas

def generateDoc(docName, title, codefilesFolderPath, docTextFilePath):

    canvas = Canvas(docName, pagesize=letter) 
    canvas.setLineWidth(.3)
    canvas.setFont('Helvetica', 12)
    canvas.drawString(30,750,'OFFICIAL COMMUNIQUE')
    canvas.save()

generateDoc("temp.pdf","","","")