Question: I have a CSV file with two columns (a and b) of data:

```
a    b
30   3000.01
5    3000.02
1    3001.01
5    3001.02

```

I am using pandas to try and select rows that only have the ".01" values in column "b".
So output should be:

```
a    b
30   3000.01
1    3001.01

```

Basically is there a way to search/select rows in column b with the specified criteria of values ending in ".01"?

Answer: 
To update anything in your cloudformation template you run an update-stack command with the new or update cloudformation template as an input parameter. AWS will then only alter the components you have changed. So if any line in the userData section has been altered when you run update-stack AWS will run through the entire userData section once again.

THis also means your EC2 instances will be destroyed and replaced by new instances if your change requires updating userData.

**Update:** You can update your EC2 instances user data without destroying if you're EC2 instance is using an EBS drive and you turn it off first. But this is an anti-pattern in my opinion. The EC2 instances is just a VM. You should keep it immutable. If something needs to change rebuild the instance.
```
"Fn::Join": [
        "/n",
        [
            "#!/bin/bash",
            "apt-get update",
            "apt-get -y upgrade",
        ]

```

actually this is the correct way. Don't know whether it is just a typo from your side