sympy/core/tests/test_str.py

   1 from sympy import Symbol, Rational, Derivative, I, log, sqrt, exp, sin
   2
   3 x = Symbol('x')
   4 y = Symbol('y')
   5 z = Symbol('z')
   6 w = Symbol('w')
   7
   8
   9 def test_pow():
  10     assert str(1/x) == "1/x"
  11
  12 def test_poly_str():
  13     #if any of these tests fails, it can still be correct, just the terms can
  14     #be in a different order. That happens for example when we change the
  15     #hash algorithm. If it is correct, just add another item in the list [] of
  16     #correct results.
  17     assert str((2*x-(7*x**2 - 2) + 3*y)) in ["2 - 7*x**2 + 2*x + 3*y",
  18             "2 + 3*y + 2*x - 7*x**2", "2 + 3*y - 7*x**2 + 2*x",
  19             "3*y + 2*x + 2 - 7*x**2", "2 + 2*x + 3*y - 7*x**2"]
  20     assert str(x-y) in ["x - y", "-y + x"]
  21     assert str(2+-x) in ["2 - x", "-x + 2"]
  22     assert str(x-2) in ["x - 2", "(-2) + x", "-2 + x"]
  23     assert str(x-y-z-w) in ["x - y - z - w","-w - y - z + x","x - w - y - z",
  24                             "-w + x - y - z","-z - w - y + x","-y + x - w - z",
  25                             "-y - z - w + x"]
  26     assert str(x-y-z-w) in [
  27             "-w - y - z + x","x - w - y - z","-w + x - z - y","-y - w - z + x",
  28             "-y + x - z - w","-y + x - w - z","-w + x - y - z","-z - w - y +x",
  29             "-y - z - w + x"]
  30     assert str(x-z*y**2*z*w) in ["-z**2*y**2*w + x", "x - w*y**2*z**2",
  31             "-y**2*z**2*w + x","x - w*z**2*y**2","x - y**2*z**2*w",
  32             "x - y**2*w*z**2","x - z**2*y**2*w","-w*z**2*y**2 + x",
  33             "-w*y**2*z**2 + x","x - z**2*w*y**2"]
  34
  35 def test_bug1():
  36     assert str(x-1*y*x*y) in ["x - x*y**2", "-x*y**2 + x"]
  37
  38 def test_bug2():
  39     e = x-y
  40     a = str(e)
  41     b = str(e)
  42     assert a == b
  43
  44 def test_bug3():
  45     x = Symbol("x")
  46     e = sqrt(x)
  47     assert str(e) == "x**(1/2)"
  48
  49 def test_bug4():
  50     x = Symbol("x")
  51     w = Symbol("w")
  52     e = -2*sqrt(x)-w/sqrt(x)/2
  53     assert str(e) not in ["(-2)*x**1/2(-1/2)*x**(-1/2)*w",
  54             "-2*x**1/2(-1/2)*x**(-1/2)*w","-2*x**1/2-1/2*x**-1/2*w"]
  55     assert str(e) in ["-2*x**(1/2) - 1/2*x**(-1/2)*w", "-2*x**(1/2) - 1/2*w*x**(-1/2)",
  56                       "-1/2*x**(-1/2)*w - 2*x**(1/2)", "-1/2*w*x**(-1/2) - 2*x**(1/2)"]
  57
  58 def test_Derivative():
  59     x = Symbol("x")
  60     y = Symbol("y")
  61
  62     e = Derivative(x**2, x, evaluate=False)
  63     assert str(e) == "D(x**2, x)"
  64
  65     e = Derivative(x**2/y, x, y, evaluate=False)
  66     assert str(e) == "D(x**2/y, x, y)"
  67
  68 def test_x_div_y():
  69     x = Symbol("x")
  70     y = Symbol("y")
  71     assert str(x/y) == "x/y"
  72     assert str(y/x) == "y/x"
  73
  74 def test_ordering():
  75     x = Symbol("x")
  76     assert str(sin(x).series(x, 0, 15)) == "x - 1/6*x**3 + (1/120)*x**5 - 1/5040*x**7 + (1/362880)*x**9 - 1/39916800*x**11 + (1/6227020800)*x**13 + O(x**15)"