[Python-ideas] Raise exception if (not) true

[Ryan Gonzalez]

In Python, you'll constantly see code like this:

```python
if x != y:
    raise ValueError('x != y!!')
```

or:

```python
if not isinstance(x,SomeType):
    raise TypeError('x is not SomeType!')
```

Assertion help a bit:

```python
assert isinstance(x,SomeType), 'x is not SomeType!'
```

Notice I said "a bit". If optimizations are on, they're disabled. In
addition, the only type of error thrown is an AssertionError.

I propose a `raise_if` function. If the given condition is True, an
exception is raised. So, the above examples would be shortened to:

```python

raise_if(x!=y, ValueError, 'x != y!!')
raise_if(not isinstance(x,SomeType),TypeError, 'x is not SomeType!')

```

There could also be a raise_if_not function that does the opposite:

```python
raise_if_not(isinstance(x,SomeType), TypeError, 'x is not SomeType!')
```

Thoughts?

-- 
Ryan
If anybody ever asks me why I prefer C++ to C, my answer will be simple:
"It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was
nul-terminated."
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