sympy/sympy — pull request #1527 by raoulb (2012-09-08 12:51:55+00:00)
Title: Escape symbol names that are python keywords during printing

Fixes issue 3394 "Symbol called lambda causes syntax error in code from python()".
This is only half of the work:

```
In [2]: 5*Symbol("lambda")+2
Out[2]: 5*lambda + 2

In [3]: python(_)
Out[3]: "lambda_ = Symbol('lambda_')\ne = 5*lambda + 2"
```