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# CLI Parameter Types
You can use several data types for the *CLI options* and *CLI arguments*, and you can add data validation requirements too.
## Data conversion
When you declare a *CLI parameter* with some type **Typer** will convert the data received in the command line to that data type.
For example:
{* docs_src/parameter_types/index/tutorial001.py hl[4] *}
In this example, the value received for the *CLI argument* `NAME` will be treated as `str`.
The value for the *CLI option* `--age` will be converted to an `int` and `--height-meters` will be converted to a `float`.
And as `female` is a `bool` *CLI option*, **Typer** will convert it to a "flag" `--female` and the counterpart `--no-female`.
And here's how it looks like:
<div class="termy">
```console
$ python main.py --help
// Notice how --age is an INTEGER and --height-meters is a FLOAT
Usage: main.py [OPTIONS] NAME
Arguments:
NAME [required]
Options:
--age INTEGER [default: 20]
--height-meters FLOAT [default: 1.89]
--female / --no-female [default: True]
--help Show this message and exit.
// Call it with CLI parameters
$ python main.py Camila --age 15 --height-meters 1.70 --female
// All the data has the correct Python type
NAME is Camila, of type: class 'str'
--age is 15, of type: class 'int'
--height-meters is 1.7, of type: class 'float'
--female is True, of type: class 'bool'
// And if you pass an incorrect type
$ python main.py Camila --age 15.3
Usage: main.py [OPTIONS] NAME
Try "main.py --help" for help.
Error: Invalid value for '--age': '15.3' is not a valid integer
// Because 15.3 is not an INTEGER (it's a float)
```
</div>
## Watch next
See more about specific types and validations in the next sections...
/// info | Technical Details
All the types you will see in the next sections are handled underneath by <a href="https://click.palletsprojects.com/en/7.x/parameters/#parameter-types" class="external-link" target="_blank">Click's Parameter Types</a>.
///
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