A typo in Series addition caused my computer to crash
I'm pretty new to pandas and made what is obviously a rookie mistake. I was attempting to add two columns together to generate a third column. What I meant to write was this:

``` python
df['Col3'] = df.Col1 + df.Col2
```

what I actually wrote was this:

``` python
df['Col3'] = df[df.Col1] + df[df.Col2]
```

This is clearly my fault and incorrect, but I assume that this shouldn't crash my computer and require a hard shutdown. I did it twice before I realized that this was the issue, both times resulted in a full crash.
