# Functions

A function is inherited from {py:class}`secsgem.secs.functionbase.SecsStreamFunction`.

Example:

```python
class SecsS02F33(SecsStreamFunction):
    _stream = 2
    _function = 33

    _data_format = [
        DATAID,
        [
            [
                RPTID,
                [VID]
            ]
        ]
    ]

    _to_host = False
    _to_equipment = True

    _has_reply = True
    _is_reply_required = True

    _is_multi_block = True
```

The data of a function can be read and manipulated with the same functionality as the variables.
{py:func}`secsgem.secs.functionbase.SecsStreamFunction.set`, {py:func}`secsgem.secs.functionbase.SecsStreamFunction.get`, {py:func}`secsgem.secs.functionbase.SecsStreamFunction.append`, the index operator and object properties.
The objects can also en- and decode themselves.

**Usage**:

```python
>>> f=secsgem.secs.functions.SecsS02F33()
>>> f.DATAID=10
>>> f.DATA.append({"RPTID": 5, "VID": ["Hello", "Hallo"]})
>>> f.DATA.append({"RPTID": 6, "VID": ["1", "2"]})
>>> f
S2F33 W
<L [2]
<U1 10 >
<L [2]
<L [2]
    <U1 5 >
    <L [2]
    <A "Hello">
    <A "Hallo">
    >
>
<L [2]
    <U1 6 >
    <L [2]
    <A "1">
    <A "2">
    >
>
>
> .
>>> f.DATA[1].VID[0]="Goodbye"
>>> f.DATA[1].VID[1]="Auf Wiedersehen"
>>> f
S2F33 W
<L [2]
<U1 10 >
<L [2]
<L [2]
    <U1 5 >
    <L [2]
    <A "Hello">
    <A "Hallo">
    >
>
<L [2]
    <U1 6 >
    <L [2]
    <A "Goodbye">
    <A "Auf Wiedersehen">
    >
>
>
> .
>>> secsgem.common.format_hex(f.encode())
'01:02:a5:01:0a:01:02:01:02:a5:01:05:01:02:41:05:48:65:6c:6c:6f:41:05:48:61:6c:6c:6f:01:02:a5:01:06:01:02:41:07:47:6f:6f:64:62:79:65:41:0f:41:75:66:20:57:69:65:64:65:72:73:65:68:65:6e'
```

The encoded data can be used as data string in a {py:class}`secsgem.hsms.HsmsMessage` together with a {py:class}`secsgem.hsms.HsmsStreamFunctionHeader`.
See {doc}`/hsms/messages`.