1 | initial version |

```
try:
E.solve_left(T)
A=E.solve_left(T)
except:
A=E.solve_left(p*T)
```

2 | No.2 Revision |

You need to handle an exception (this is Python feature inherited in Sage):

```
try:
E.solve_left(T)
A=E.solve_left(T)
except:
A=E.solve_left(p*T)
```

3 | No.3 Revision |

You need to handle an exception (this is Python feature inherited in Sage):

```
try:
```~~E.solve_left(T)
~~A=E.solve_left(T)
except:
A=E.solve_left(p*T)

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