I am trying to parse with argparse. I have a optional argument, called TileScheme:

```
parser.add_argument("--TileScheme", "--TS", default = PuertoRico2018)

```

I want to use the input from this argument as an object, so I do this:

```
TileScheme = eval(args.TileScheme)

```

However, because its an optional argument with a default value, I often don't want to write in the optional argument. I want to pass just numeric values. However, I get this error message when I do that:

```
TypeError: eval() arg 1 must be a string or code object

```

It says this even though that eval() is modifying an optional argument! What to do???

Cheers! O.Fried