how to create a pie chart with pyqt in python

问题

Trying to create a pie chart shape but for some reason I can't get it to join together correctly. When I run my code It creates a lot of segments on top of each other. Here is my code:

from PyQt4.QtCore import *
from PyQt4.QtGui import *
import sys, random


app = QApplication(sys.argv)
scene = QGraphicsScene()
families = [1,2,3,4,5,6,7]
total = 0
colours = []
set_angle = 0
count1 = 0
total = sum(families)
for count in range(len(families)):
    number = []
    for count in range(3):
        number.append(random.randrange(0, 255))
    colours.append(QColor(number[0],number[1],number[2]))


for family in families:    
    angle = round(family/total*16*360)
    ellipse = QGraphicsEllipseItem(0,0,400,400)
    ellipse.setPos(0,0)
    ellipse.setStartAngle(set_angle)
    ellipse.setSpanAngle(angle)
    ellipse.setBrush(colours[count1])
    set_angle = angle
    count1 +=1
    scene.addItem(ellipse)
view = QGraphicsView(scene)
view.show()
app.exec_()

回答1:

Digging this thread as it might help others. @Barry's answer is almost correct, but needs a few adjustments.

Indeed, to have a perfect round shape to your ellipse, you need to change the line:

set_angle = angle

set_angle += angle

This way, the set_angle (which is the starting angle of our "pie chunks") is always the last angle drawn on the canvas.

Also, the line:

angle = round(family/total*16*360)

could be written like this (for readability's sake):

angle = round(float(family*(16*360))/total)

So a working example would be (using Python3 & PyQt5):

from PyQt5.QtWidgets import QGraphicsScene, QApplication, QGraphicsView, QGraphicsEllipseItem
from PyQt5.Qt import QColor
import sys, random


app = QApplication(sys.argv)
scene = QGraphicsScene()

families = [1,2,3,4,5,6,7,8,9,10]
total = 0
set_angle = 0
count1 = 0
colours = []
total = sum(families)

for count in range(len(families)):
    number = []
    for count in range(3):
        number.append(random.randrange(0, 255))
    colours.append(QColor(number[0],number[1],number[2]))

for family in families:
    # Max span is 5760, so we have to calculate corresponding span angle
    angle = round(float(family*5760)/total)
    ellipse = QGraphicsEllipseItem(0,0,400,400)
    ellipse.setPos(0,0)
    ellipse.setStartAngle(set_angle)
    ellipse.setSpanAngle(angle)
    ellipse.setBrush(colours[count1])
    set_angle += angle
    count1 += 1
    scene.addItem(ellipse)

view = QGraphicsView(scene)
view.show()
app.exec_()

Hope it helps.

回答2:

The problem is related to integer division, check this line: angle = round(family/total*16*360), it could be fixed setting total = float(sum(families)) or putting this line from __future__ import division at the start of your code, both solutions are valid.