import math import unittest class PowTest(unittest.TestCase): def powtest(self, type): if type != float: for i in range(-1000, 1000): self.assertEqual(pow(type(i), 0), 1) self.assertEqual(pow(type(i), 1), type(i)) self.assertEqual(pow(type(0), 1), type(0)) self.assertEqual(pow(type(1), 1), type(1)) for i in range(-100, 100): self.assertEqual(pow(type(i), 3), i*i*i) pow2 = 1 for i in range(0, 31): self.assertEqual(pow(2, i), pow2) if i != 30 : pow2 = pow2*2 for i in list(range(-10, 0)) + list(range(1, 10)): ii = type(i) inv = pow(ii, -1) # inverse of ii for jj in range(-10, 0): self.assertAlmostEqual(pow(ii, jj), pow(inv, -jj)) for othertype in int, float: for i in range(1, 100): zero = type(0) exp = -othertype(i/10.0) if exp == 0: continue self.assertRaises(ZeroDivisionError, pow, zero, exp) il, ih = -20, 20 jl, jh = -5, 5 kl, kh = -10, 10 asseq = self.assertEqual if type == float: il = 1 asseq = self.assertAlmostEqual elif type == int: jl = 0 elif type == int: jl, jh = 0, 15 for i in range(il, ih+1): for j in range(jl, jh+1): for k in range(kl, kh+1): if k != 0: if type == float or j < 0: self.assertRaises(TypeError, pow, type(i), j, k) continue asseq( pow(type(i),j,k), pow(type(i),j)% type(k) ) def test_powint(self): self.powtest(int) def test_powfloat(self): self.powtest(float) def test_other(self): # Other tests-- not very systematic self.assertEqual(pow(3,3) % 8, pow(3,3,8)) self.assertEqual(pow(3,3) % -8, pow(3,3,-8)) self.assertEqual(pow(3,2) % -2, pow(3,2,-2)) self.assertEqual(pow(-3,3) % 8, pow(-3,3,8)) self.assertEqual(pow(-3,3) % -8, pow(-3,3,-8)) self.assertEqual(pow(5,2) % -8, pow(5,2,-8)) self.assertEqual(pow(3,3) % 8, pow(3,3,8)) self.assertEqual(pow(3,3) % -8, pow(3,3,-8)) self.assertEqual(pow(3,2) % -2, pow(3,2,-2)) self.assertEqual(pow(-3,3) % 8, pow(-3,3,8)) self.assertEqual(pow(-3,3) % -8, pow(-3,3,-8)) self.assertEqual(pow(5,2) % -8, pow(5,2,-8)) for i in range(-10, 11): for j in range(0, 6): for k in range(-7, 11): if j >= 0 and k != 0: self.assertEqual( pow(i,j) % k, pow(i,j,k) ) if j >= 0 and k != 0: self.assertEqual( pow(int(i),j) % k, pow(int(i),j,k) ) def test_big_exp(self): import random self.assertEqual(pow(2, 50000), 1 << 50000) # Randomized modular tests, checking the identities # a**(b1 + b2) == a**b1 * a**b2 # a**(b1 * b2) == (a**b1)**b2 prime = 1000000000039 # for speed, relatively small prime modulus for i in range(10): a = random.randrange(1000, 1000000) bpower = random.randrange(1000, 50000) b = random.randrange(1 << (bpower - 1), 1 << bpower) b1 = random.randrange(1, b) b2 = b - b1 got1 = pow(a, b, prime) got2 = pow(a, b1, prime) * pow(a, b2, prime) % prime if got1 != got2: self.fail(f"{a=:x} {b1=:x} {b2=:x} {got1=:x} {got2=:x}") got3 = pow(a, b1 * b2, prime) got4 = pow(pow(a, b1, prime), b2, prime) if got3 != got4: self.fail(f"{a=:x} {b1=:x} {b2=:x} {got3=:x} {got4=:x}") def test_bug643260(self): class TestRpow: def __rpow__(self, other): return None None ** TestRpow() # Won't fail when __rpow__ invoked. SF bug #643260. def test_bug705231(self): # -1.0 raised to an integer should never blow up. It did if the # platform pow() was buggy, and Python didn't worm around it. eq = self.assertEqual a = -1.0 # The next two tests can still fail if the platform floor() # function doesn't treat all large inputs as integers # test_math should also fail if that is happening eq(pow(a, 1.23e167), 1.0) eq(pow(a, -1.23e167), 1.0) for b in range(-10, 11): eq(pow(a, float(b)), b & 1 and -1.0 or 1.0) for n in range(0, 100): fiveto = float(5 ** n) # For small n, fiveto will be odd. Eventually we run out of # mantissa bits, though, and thereafer fiveto will be even. expected = fiveto % 2.0 and -1.0 or 1.0 eq(pow(a, fiveto), expected) eq(pow(a, -fiveto), expected) eq(expected, 1.0) # else we didn't push fiveto to evenness def test_negative_exponent(self): for a in range(-50, 50): for m in range(-50, 50): with self.subTest(a=a, m=m): if m != 0 and math.gcd(a, m) == 1: # Exponent -1 should give an inverse, with the # same sign as m. inv = pow(a, -1, m) self.assertEqual(inv, inv % m) self.assertEqual((inv * a - 1) % m, 0) # Larger exponents self.assertEqual(pow(a, -2, m), pow(inv, 2, m)) self.assertEqual(pow(a, -3, m), pow(inv, 3, m)) self.assertEqual(pow(a, -1001, m), pow(inv, 1001, m)) else: with self.assertRaises(ValueError): pow(a, -1, m) with self.assertRaises(ValueError): pow(a, -2, m) with self.assertRaises(ValueError): pow(a, -1001, m) if __name__ == "__main__": unittest.main()