# otp.Source.write_parquet

#### Source.write_parquet(output_path, compression_type='snappy', num_tick_per_row_group=1000, partitioning_keys='', propagate_input_ticks=False, inplace=False)

Writes the input tick series to parquet data file.

Input must not have field 'time' as that field will also be added by the EP in the resulting file(s)

* **Parameters:**
  * **output_path** ([*str*](https://docs.python.org/3/library/stdtypes.html#str)) -- Path for saving ticks to Parquet file.
    Partitioned: Path to the root directory of the parquet files.
    Non-partitioned: Path to the parquet file.
  * **compression_type** ([*str*](https://docs.python.org/3/library/stdtypes.html#str)) -- Compression type for parquet files.
    Should be one of these: gzip, lz4, none, snappy (default), zstd.
  * **num_tick_per_row_group** ([*int*](https://docs.python.org/3/library/functions.html#int)) -- Number of rows per row group.
  * **partitioning_keys** ([*list*](https://docs.python.org/3/library/stdtypes.html#list) *,* [*str*](https://docs.python.org/3/library/stdtypes.html#str)) -- 

    List of fields (list or comma-separated string) to be used as keys for partitioning.

    Setting this parameter will switch this EP to partitioned mode.

    In non-partitioned mode, if the path points to a file that already exists, it will be overridden.
    When partitioning is active:
    * The target directory must be empty
    * Key fields and their string values will be automatically URL-encoded to avoid conflicts with
      : filesystem naming rules.

    Pseudo-fields '_SYMBOL_NAME' and '_TICK_TYPE' may be used as partitioning_keys and
    will be added to the schema automatically.
  * **propagate_input_ticks** ([*bool*](https://docs.python.org/3/library/functions.html#bool)) -- Switches propagation of the ticks. If set to True, ticks will be propagated.
  * **inplace** ([*bool*](https://docs.python.org/3/library/functions.html#bool)) -- A flag controls whether operation should be applied inplace.
    If `inplace=True`, then it returns nothing. Otherwise method
    returns a new modified object.

### Examples

Simple usage:

```pycon
>>> data = otp.Ticks(A=[1, 2, 3])
>>> data = data.write_parquet("/path/to/parquet/file")  
>>> otp.run(data)  
```

#### SEE ALSO
**WRITE_TO_PARQUET** OneTick event processor
<br/>
[`onetick.py.ReadParquet`](../sources/read_parquet.md#onetick.py.ReadParquet)
<br/>