RFC: Refactor GAMWriter._dump

- Use `io.StringIO()`
- Fine tune `np.array2string`
- Add tests for `to_gam`
- Also add `from_gam_string` and `from_gam_url`

Author: oyamad

quantecon/game_theory/game_converters.py

@@ -27,6 +27,8 @@
   [[-19., -19.,   1.],   [ -8.,  -8.,   2.],   [  3.,   3.,   3.]]]]
 
 """
+import io
+import sys
 import numbers
 import numpy as np
 from .normal_form_game import Player, NormalFormGame
@@ -326,17 +328,27 @@ def to_string(cls, g):
 
     @staticmethod
     def _dump(g):
-        s = str(g.N) + '\n'
-        s += ' '.join(map(str, g.nums_actions)) + '\n\n'
+        p = GAMPayoffVector.from_nfg(g)
 
-        for i, player in enumerate(g.players):
-            payoffs = np.array2string(
-                player.payoff_array.transpose(
-                    (*range(g.N-i, g.N), *range(g.N-i))
-                ).ravel(order='F'))[1:-1]
-            s += ' '.join(payoffs.split()) + ' '
+        buf = io.StringIO()
+
+        buf.write(str(p.N))
+        buf.write("\n")
+        buf.write(" ".join(map(str, p.nums_actions)))
+        buf.write("\n\n")
+
+        payoffs_str = np.array2string(
+            p.payoffs,
+            separator=" ",
+            threshold=sys.maxsize,  # no truncation '...'
+            # suppress_small helps avoid scientific notation for small |x|;
+            # large |x| values may still print with e+...
+            suppress_small=True
+        )[1:-1]  # strip brackets
+
+        buf.write(" ".join(payoffs_str.split()))
 
-        return s.rstrip()
+        return buf.getvalue().rstrip()
 
 
 def from_gam(filename: str) -> NormalFormGame:
@@ -364,6 +376,14 @@ def from_gam(filename: str) -> NormalFormGame:
     return GAMReader.from_file(filename)
 
 
+def from_gam_string(string):
+    return GAMReader.from_string(string)
+
+
+def from_gam_url(url):
+    return GAMReader.from_url(url)
+
+
 def to_gam(g, file_path=None):
     """
     Write a NormalFormGame to a file in .gam format.

quantecon/game_theory/tests/test_game_converters.py

@@ -104,7 +104,7 @@ def test_invalid_inputs():
     assert_raises(ValueError, GAMPayoffVector, (2, 2), np.zeros(7))
 
 
-# TestGAMWriter #
+# GAMWriter/to_gam #
 
 class TestGAMWriter:
     def setup_method(self):
@@ -157,3 +157,27 @@ def test_to_gam(self):
         assert_string_equal(s_actual, self.s_desired + '\n')
 
         os.remove(temp_path)
+
+
+def test_gam_writer_many_actions():
+    n0, n1 = 40, 60
+    p0 = Player(np.arange(n0 * n1).reshape(n0, n1))
+    p1 = Player((np.arange(n1 * n0) + 10_000).reshape(n1, n0))
+    g = NormalFormGame((p0, p1))
+
+    s = to_gam(g)
+
+    # NumPy summary marker should never appear
+    assert_('...' not in s)
+
+    # Token count matches N * prod(nums_actions)
+    tokens = s.split()
+    N = int(tokens[0])
+    nums_actions = tuple(int(x) for x in tokens[1:1+N])
+    payoff_tokens = tokens[1+N:]
+
+    assert_(N == 2)
+    assert_(nums_actions == (n0, n1))
+
+    expected = N * np.prod(nums_actions)
+    assert_(len(payoff_tokens) == expected)