21.2 Drawing graphs on canvas

You can also achieve the same effect by passing the canvas object to the area.T.draw() method explicitly:

can = canvas.init("foo.pdf")
...
ar = area.T(...)
ar.draw(can)

You can also pass a file object (or file-like object, such as StringIO) to canvas.init. In this case, you need to define the output format via the second argument.

fd = file("foo.pdf", "w")
can = canvas.init(fd, "pdf")
...
ar.draw(can)

Naturally, you can write to multiple files by passing multiple canvas objects to different area.T.draw(). For example, the below example draws the first chart to graph1.pdf and the next chart to graph2.pdf.

#
# Copyright (C) 2000-2005 by Hewlett Packard Development Company, LP 
# 
# Author: Yasushi Saito (yasushi.saito@hp.com)
#
# Jockey is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2, or (at your option) any
# later version.
#
# Jockey is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
#
#
# Draw two charts, graph1.pdf and graph2.pdf.
#
from pychart import *

can = canvas.init("graph1.pdf")
data = chart_data.read_csv("lines.csv")
ar = area.T(x_range = (0,100), y_range = (0,100),
            x_axis = axis.X(label="X", tic_interval=10),
            y_axis = axis.Y(label="Y", tic_interval=10))
eb = error_bar.error_bar2(tic_len=5, hline_style=line_style.gray50)
ar.add_plot(line_plot.T(label="foo", data=data, error_bar=eb, y_error_minus_col=3),
            line_plot.T(label="bar", data=data, ycol=2, error_bar=eb, y_error_minus_col=3))
ar.draw(can)
tb = text_box.T(loc=(40, 130), text="This is\nimportant!", line_style=None)
tb.add_arrow((ar.x_pos(data[6][0]), ar.y_pos(data[6][1])), "cb")
tb.draw(can)

can = canvas.init("graph2.pdf")
ar = area.T(loc=(200, 0), x_range=(0,100), y_range=(0,100),
            x_axis = axis.X(label="X", tic_interval=10),
            y_axis = axis.Y(label="Y", tic_interval=10))
ar.add_plot(line_plot.T(label="foo", data=data, data_label_format="/8{}%d"),
            line_plot.T(label="bar", data=data, ycol=2))
ar.draw(can)

# Note: can.close() is called automatically for every open canvas.