Add REPL that evaluates code on various Python versions

repl.py

@@ -0,0 +1,86 @@
+"""A repl across hosts."""
+import ast
+import sys
+import readline
+import traceback
+from io import StringIO
+
+
+def read_stmt():
+    stmt = ''
+    prompt = '>>> '
+    indented = False
+    while True:
+        try:
+            line = input(prompt)
+        except EOFError:
+            print()
+            sys.exit(0)
+        stmt += line + '\n'
+        try:
+            ast.parse(stmt)
+        except SyntaxError as e:
+            msg = e.args[0]
+            if msg == 'unexpected EOF while parsing':
+                prompt = '... '
+                continue
+            raise
+        else:
+            if line.startswith((' ', '\t')) and prompt == '... ':
+                continue
+            return stmt
+
+
+namespace = {}
+
+def runit(stmt):
+    code = compile(stmt, '<stdin>', 'single', dont_inherit=True)
+    sys.stdout = StringIO()
+    try:
+        result = exec(code, namespace)
+    except Exception:
+        return False, traceback.format_exc()
+    return True, sys.stdout.getvalue()
+
+
+def dorepl(group):
+    from chopsticks.tunnel import ErrorResult
+    try:
+        stmt = read_stmt()
+    except Exception:
+        traceback.print_exc()
+        return
+    results = group.call(runit, stmt)
+    vals = list(results.values())
+    if all(vals[0] == v for v in vals[1:]):
+        results = {'all %d' % len(vals): vals[0]}
+    for host, result in sorted(results.items()):
+        if isinstance(result, ErrorResult):
+            success = False
+            result = result.msg
+        else:
+            success, result = result
+        color = '32' if success else '31'
+        if sys.stderr.isatty():
+            fmt = '\x1b[{color}m[{host}]\x1b[0m {l}'
+        else:
+            fmt = '[{host}] {l}'
+
+        for l in result.splitlines():
+            print(fmt.format(host=host, color=color, l=l))
+
+
+if __name__ == '__main__':
+    from chopsticks.tunnel import Docker
+    from chopsticks.group import Group
+    group = Group([
+        Docker('python3.4', image='python:3.4'),
+        Docker('python3.5', image='python:3.5'),
+        Docker('python3.6', image='python:3.6'),
+    ])
+
+    try:
+        while True:
+            dorepl(group)
+    finally:
+        del group