draws circle using ASCII characters

circle.py

#!/usr/bin/env python
#
# circle.py - draws circle using ASCII characters
#
# http://kldp.org/node/135436
#
# Seungwon Jeong <seungwon0@gmail.com>
#
# Copyright (C) 2012 by Seungwon Jeong
#
# This program 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 3 of the License, or
# (at your option) any later version.
#
# This program 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.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see
# <http://www.gnu.org/licenses/>.

import sys

def circle(r):
    tolerance = r * 0.8

    rows = list()
    for y in range(-r, r + 1):
        row = list()
        for x in range(-r, r + 1):
            value = x * x + y * y - r * r
            if value >= -tolerance and value <= tolerance:
                row.append('*')
            else:
                row.append('.')

        rows.append(''.join(row))

    return "\n".join(rows)

if __name__ == '__main__':
    if len(sys.argv) != 2:
        print 'Usage: %s r' % (sys.argv[0])
        sys.exit(2)

    r = int(sys.argv[1])
    print circle(r)

test_circle.py

#!/usr/bin/env python
#
# test_circle.py - tests circle.py
#
# http://kldp.org/node/135436
#
# Seungwon Jeong <seungwon0@gmail.com>
#
# Copyright (C) 2012 by Seungwon Jeong
#
# This program 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 3 of the License, or
# (at your option) any later version.
#
# This program 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.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see
# <http://www.gnu.org/licenses/>.

import unittest

import circle

class CircleTest(unittest.TestCase):
    circle1 = '''\
.*.
*.*
.*.'''
    circle2 = '''\
.***.
*...*
*...*
*...*
.***.'''
    circle3 = '''\
..***..
.*...*.
*.....*
*.....*
*.....*
.*...*.
..***..'''
    circle4 = '''\
...***...
.**...**.
.*.....*.
*.......*
*.......*
*.......*
.*.....*.
.**...**.
...***...'''
    circle7 = '''\
.....*****.....
...**.....**...
..*.........*..
.*...........*.
.*...........*.
*.............*
*.............*
*.............*
*.............*
*.............*
.*...........*.
.*...........*.
..*.........*..
...**.....**...
.....*****.....'''

    def testCircle(self):
        self.assertEqual(circle.circle(1), self.circle1, 'r = 1')
        self.assertEqual(circle.circle(2), self.circle2, 'r = 2')
        self.assertEqual(circle.circle(3), self.circle3, 'r = 3')
        self.assertEqual(circle.circle(4), self.circle4, 'r = 4')
        self.assertEqual(circle.circle(7), self.circle7, 'r = 7')

if __name__ == '__main__':
    unittest.main()