Fix things like foolambda being parsed as a lambda declaration

Closes #109

electric-operator.el

@@ -862,14 +862,16 @@ Also handles C++ lambda capture by reference."
 
 (defun electric-operator-python-mode-in-lambda-args? ()
   "Are we inside the arguments statement of a lambda?"
-  (electric-operator-looking-back-locally "lambda[^:]*"))
+  ;; \\(\\s-\\|^\\) instead of just \\b because otherwise foo_lambda matches
+  (electric-operator-looking-back-locally "\\(\\s-\\|^\\)lambda[^:]*"))
 
 (defun electric-operator-python-mode-: ()
   "Handle python dict assignment"
   (cond
    ((electric-operator-python-mode-in-lambda-args?) ": ")
 
-   ;; A keyword statement (we can't use \\b here because it matches _)
+   ;; A keyword statement (we need \\(\\s-\\|^\\) instead of \\b here not not
+   ;; match _)
    ((electric-operator-looking-back-locally "\\(\\s-\\|^\\)\\(if\\|elif\\|else\\|for\\|while\\|class\\|def\\|try\\|except\\|with\\)") ":")
 
    ;; type definition inside a function

features/python-mode.feature

@@ -160,6 +160,13 @@ Feature: Python mode basics
     When I type "lambda x=y[1:5]:print x"
     Then I should see "lambda x=y[1:5]: print x"
 
+  Scenario: Lambda inside another word doesn't affect spacing
+    When I type "foolambdabar=1"
+    Then I should see "foolambdabar = 1"
+
+  Scenario: Lambda inside another word with _ doesn't affect spacing
+    When I type "foo_lambdabar=1"
+    Then I should see "foo_lambdabar = 1"
 
   # Slice operator
   Scenario: Don't space : inside slices