src/UserGuide/latest/QuickStart/InterfaceDefinition/InterfaceDefinition-Python.md

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# Interface Definitions - Python

## Schema

```Python

class TSDataType(IntEnum):
    """
    Enumeration of data types currently supported by TsFile.
    """
    BOOLEAN = 0
    INT32 = 1
    INT64 = 2
    FLOAT = 3
    DOUBLE = 4
    TEXT = 5
    TIMESTAMP = 8
    DATE = 9
    BLOB = 10
    STRING = 11

class TSEncoding(IntEnum):
    """
    Value encoding accepted by the writer. The comment after each
    member lists the data types it can be used with.
    """
    PLAIN = 0         # all types
    DICTIONARY = 1    # STRING, TEXT
    RLE = 2           # INT32, INT64, TIMESTAMP, DATE
    TS_2DIFF = 4      # INT32, INT64, TIMESTAMP, DATE, FLOAT, DOUBLE
    GORILLA = 8       # INT32, INT64, TIMESTAMP, DATE, FLOAT, DOUBLE
    ZIGZAG = 9        # INT32, INT64
    SPRINTZ = 12      # INT32, INT64, FLOAT, DOUBLE

class Compressor(IntEnum):
    """
    Compression accepted by the writer. The default is LZ4.
    """
    UNCOMPRESSED = 0
    SNAPPY = 1
    GZIP = 2
    LZO = 3
    LZ4 = 7

class ColumnCategory(IntEnum):
    """
    Enumeration of column categories in TsFile.
    TAG: a tag column (part of the device identifier / joint primary key).
    FIELD: a field column, holding the measured values.
    ATTRIBUTE / TIME: reserved column roles.
    """

    TAG = 0
    FIELD = 1
    ATTRIBUTE = 2
    TIME = 3

class ColumnSchema:
    """Defines schema for a table column (name, datatype, category)."""

    column_name = None
    data_type = None
    category = None

    def __init__(self, column_name: str, data_type: TSDataType, 
                 category: ColumnCategory = ColumnCategory.FIELD)

class TableSchema:
    """Schema definition for a table structure."""
    
    table_name = None
    columns = None

    def __init__(self, table_name: str, columns: List[ColumnSchema])


class ResultSetMetaData:
    """Metadata container for query result sets (columns, types, table name)."""
    
    column_list = None
    data_types = None
    table_name = None

    def __init__(self, column_list: List[str], data_types: List[TSDataType])

```



## Write interface

### TsFileWriter 

```python
class TsFileTableWriter:
    """
    Facilitates writing structured table data into a TsFile with a specified schema.
    """

    
    """
    :param path: The path of tsfile, will create if it doesn't exist.
    :param table_schema: describes the schema of the tables want to write.
    :param memory_threshold: bytes buffered before an automatic flush (default 128MB).
    :return: no return value.
    """
    def __init__(self, path: str, table_schema: TableSchema,
                 memory_threshold: int = 128 * 1024 * 1024)


    """
    Write a tablet into table in tsfile.
    :param tablet: stored batch data of a table.
    :return: no return value.
    """
    def write_table(self, tablet: Tablet)

    """
    Write a pandas DataFrame into the table. Column encoding/compression follow
    the table schema (or the engine defaults).
    :param dataframe: the data to write.
    :return: no return value.
    """
    def write_dataframe(self, dataframe: pandas.DataFrame)

    """
    Flush buffered data to disk.
    :return: no return value.
    """
    def flush(self)

    """
    Close TsFileTableWriter and flush data automatically.
    :return: no return value.
    """
    def close(self)

    # Usable as a context manager:
    #   with TsFileTableWriter(path, schema) as w:
    #       w.write_table(tablet)
    def __enter__(self)
    def __exit__(self, exc_type, exc_val, exc_tb)
```



### Tablet definition

```Python
class Tablet(object)
    """
    A pre-allocated columnar data container for batch data with type constraints.
    Creates timestamp buffer and typed data columns, with value range validation ranges
    for numeric types.

    Initializes:
    :param column_name_list: name list for data columns.
    :param type_list: TSDataType values specifying allowed types per column.
    :param max_row_num: Pre-allocated row capacity (default 1024)
    :return: no return value.
    """

    def __init__(self, column_name_list: list[str], type_list: list[TSDataType],
                 max_row_num: int = 1024)
    
```

### dataframe_to_tsfile

```python
def dataframe_to_tsfile(dataframe: pd.DataFrame,
                        file_path: str,
                        table_name: Optional[str] = None,
                        time_column: Optional[str] = None,
                        tag_column: Optional[list[str]] = None)
    """
    Write a pandas DataFrame to a TsFile.

    :param dataframe:   the data to write.
    :param file_path:   destination .tsfile path.
    :param table_name:  output table name.
    :param time_column: name of the column to use as the timestamp column.
    :param tag_column:  names of the columns to treat as TAG columns.
    """
```

## Configuration

Global write defaults — the default per-type encodings, the default compression,
and the time-column encoding/compression — are exposed as a single dictionary.
Change them **before** creating a writer.

```python
from tsfile import get_tsfile_config, set_tsfile_config
from tsfile import TSEncoding, Compressor

cfg = get_tsfile_config()          # -> dict of all config values
# e.g. cfg["default_compression_type_"], cfg["int64_encoding_type_"],
#      cfg["time_encoding_type_"], cfg["time_compress_type_"], ...

set_tsfile_config({
    "default_compression_type_": Compressor.LZ4,
    "int64_encoding_type_": TSEncoding.TS_2DIFF,
})
```

`set_tsfile_config` validates each value and only updates the keys you pass.
Encoding/compression values are `TSEncoding` / `Compressor` members. The allowed
encodings per data type, and the default used when you do not change it:

| Data type | Allowed encodings | Default |
|---|---|---|
| `BOOLEAN` | `PLAIN` | `PLAIN` |
| `INT32`, `INT64`, `DATE` | `PLAIN`, `TS_2DIFF`, `GORILLA`, `ZIGZAG`, `RLE`, `SPRINTZ` | `TS_2DIFF` |
| `FLOAT`, `DOUBLE` | `PLAIN`, `TS_2DIFF`, `GORILLA`, `SPRINTZ` | `GORILLA` |
| `STRING`, `TEXT` | `PLAIN`, `DICTIONARY` | `PLAIN` |

Compression applies to any data type: `UNCOMPRESSED`, `SNAPPY`, `GZIP`, `LZO`, or `LZ4` (default `LZ4`).

## Read Interface

### TsFileReader

```python
class TsFileReader:
    """
    Query table data from a TsFile.
    """
    
    """
    Initialize a TsFile reader for the specified file path.
    :param pathname: The path to the TsFile.
    :return  no return value.
    """
    def __init__(self, pathname)


    """
    Executes a time range query on the specified table and columns.

    :param table_name: The name of the table to query.
    :param column_names: A list of column names to retrieve.
    :param start_time: The start time of the query range (default: minimum int64 value).
    :param end_time: The end time of the query range (default: maximum int64 value).
    :return: A query result set handler.
    """
    def query_table(self, table_name : str, column_names : List[str],
                    start_time : int = np.iinfo(np.int64).min, 
                    end_time: int = np.iinfo(np.int64).max) -> ResultSet

    """
    Execute a table query by row, with offset/limit pushdown and an optional
    tag filter. A TAG predicate restricts the query to the devices whose
    TAG-column values match. Build a filter with the helpers in tsfile.tag_filter
    (tag_eq, tag_neq, tag_lt, tag_lteq, tag_gt, tag_gteq, tag_between, ...) and
    combine filters with &, | and ~.

    :param table_name: The name of the table to query.
    :param column_names: A list of column names to retrieve.
    :param offset: Number of leading rows to skip (default 0).
    :param limit: Maximum number of rows to return; < 0 means unlimited.
    :param tag_filter: Optional tag predicate (TagFilter), or None for no filtering.
    :param batch_size: <= 0 returns rows one by one; > 0 returns blocks of that size.
    :return: A query result set handler.
    """
    def query_table_by_row(self, table_name : str, column_names : List[str],
                           offset : int = 0, limit : int = -1,
                           tag_filter = None, batch_size : int = 0) -> ResultSet

    """
    Retrieves the schema of the specified table.

    :param table_name: The name of the table.
    :return: The schema of the specified table.
    """
    def get_table_schema(self, table_name : str)-> TableSchema


    """
    Retrieves the schemas of all tables in the TsFile.

    :return: A dictionary mapping table names to their schemas.
    """
    def get_all_table_schemas(self) ->dict[str, TableSchema]


    """
    Closes the TsFile reader. If the reader has active result sets, they will be invalidated.
    """
    def close(self)

```

### ResultSet



```python
class ResultSet:
    """
    Retrieves data from a query result set. When a query is executed, a query handler is returned.
    If the reader is closed, the result set will become invalid.
    """

    """
    Checks and moves to the next row in the query result set.

    :return: True if the next row exists, False otherwise.
    """
    def next(self) -> bool


    """
    Retrieves the column information of the result set.

    :return: A dictionary containing column names as keys and their data types as values.
    """
    def get_result_column_info(self) -> dict[str, TsDataType]

    
    """
    Fetches the next DataFrame from the query result set.

    :param max_row_num: The maximum number of rows to retrieve. Default is 1024.
    :return: A DataFrame containing data from the query result set.
    """
    def read_data_frame(self, max_row_num : int = 1024) -> DataFrame

    
    """
    Retrieves the value at the specified index from the query result set.

    :param index: The index of the value to retrieve, 1 <= index <= column_num.
    :return: The value at the specified index.
    """
    def get_value_by_index(self, index : int)

      
    """
    Retrieves the value for the specified column name from the query result set.

    :param column_name: The name of the column to retrieve the value from.
    :return: The value of the specified column.
    """
    def get_value_by_name(self, column_name : str)

      
	
    """
    Retrieves the metadata of the result set.

    :return: The metadata of the result set as a ResultSetMetadata object.
    """
    def get_metadata(self) -> ResultSetMetadata
      
    
    """
    Checks whether the field at the specified index in the result set is null.

    :param index: The index of the field to check.  1 <= index <= column_num.
    :return: True if the field is null, False otherwise.
    """
    def is_null_by_index(self, index : int)

      
      
    """
    Checks whether the field with the specified column name in the result set is null.

    :param name: The name of the column to check.
    :return: True if the field is null, False otherwise.
    """
    def is_null_by_name(self, name : str)

      
    """
    Closes the result set and releases any associated resources.
    """
    def close(self)
```

### to_dataframe

```python

def to_dataframe(file_path: str,
                 table_name: Optional[str] = None,
                 column_names: Optional[list[str]] = None,
                 start_time: Optional[int] = None,
                 end_time: Optional[int] = None,
                 max_row_num: Optional[int] = None,
                 as_iterator: bool = False) -> Union[pd.DataFrame, Iterator[pd.DataFrame]]:

    """
       Read data from a TsFile and convert it into a Pandas DataFrame or
       an iterator of DataFrames.

       Users can filter data by table name, column names, time range,
       and maximum number of rows.

       Parameters
       ----------
       file_path : str
           Path to the TsFile to be read.

       table_name : Optional[str], default None
           Name of the table to query in table-model TsFiles.
           If None and the file is in table model, the first table
           found in the schema will be used.

       column_names : Optional[list[str]], default None
           List of column/measurement names to query.
           - If None, all columns will be returned.
           - Column existence will be validated in table-model TsFiles.

       start_time : Optional[int], default None
           Start timestamp for the query.
           If None, the minimum int64 value is used.

       end_time : Optional[int], default None
           End timestamp for the query.
           If None, the maximum int64 value is used.

       max_row_num : Optional[int], default None
           Maximum number of rows to read.
           - If None, all available rows will be returned.
           - When `as_iterator` is False, the final DataFrame will be
             truncated to this size if necessary.

       as_iterator : bool, default False
           Whether to return an iterator of DataFrames instead of
           a single concatenated DataFrame.
           - True: returns an iterator yielding DataFrames in batches
           - False: returns a single Pandas DataFrame

       Returns
       -------
       Union[pandas.DataFrame, Iterator[pandas.DataFrame]]
           - A Pandas DataFrame if `as_iterator` is False
           - An iterator of Pandas DataFrames if `as_iterator` is True

       Raises
       ------
       TableNotExistError
           If the specified table name does not exist in a table-model TsFile.

       ColumnNotExistError
           If any specified column does not exist in the table schema.
       """
```