λ's

python/lambdas/lambdas.py

@@ -0,0 +1,82 @@
+import ast
+import inspect
+
+FUNC_NAME = "__lambda__"
+
+def λ(*args):
+    prev_frame = inspect.currentframe().f_back
+
+    body = ast.parse(args[-1], "<lambda>", "exec").body
+    args = args[:-1]
+
+    def make_arg(a):
+        a = ast.arg(a, None, None)
+        a.lineno = 0
+        a.col_offset = 0
+        return a
+
+    arguments = ast.arguments(posonlyargs=[],
+                              args=[make_arg(a) for a in args],
+                              kwonlyargs=[], kw_defaults=[], defaults=[])
+    arguments.lineno = 0
+    arguments.col_offset = 0
+    func = ast.FunctionDef(FUNC_NAME, arguments, body, [])
+    func.lineno = 0
+    func.col_offset = 0
+    toplevel = ast.Interactive([func])
+    toplevel.lineno = 0
+    toplevel.col_offset = 0
+    func = compile(toplevel, "<lambda>", "single")
+
+    exec(func, prev_frame.f_globals, prev_frame.f_locals)
+    func = prev_frame.f_locals[FUNC_NAME]
+    del prev_frame.f_locals[FUNC_NAME]
+
+    return func
+
+
+# Examples:
+#
+# λ("""print("haha multiline lambdas")
+# return 1337""")()
+#
+# --------------------------------------
+#
+# λ("a", "b", "c", """if a:
+#     return b
+# else:
+#     return c""")(False, 1, 2)
+#
+# --------------------------------------
+#
+# meow = 10
+# λ("a", "b", "c", """if a:
+#     return b + meow
+# else:
+#     return c + meow""")(False, 1, 2)
+#
+# --------------------------------------
+#
+# def my_func():
+#     meow = 20
+#     return λ("cnd", """if cnd:
+#     return meow
+# else:
+#     return 'nope'""")
+#
+# meow = 30
+# my_func()(True)
+#
+# --------------------------------------
+#
+# def my_func():
+#     meow = 20
+#     return λ("cnd", """global meow
+# if cnd:
+#     return meow
+# else:
+#     return 'nope'""")
+#
+# meow = 30
+# my_func()(True)
+#