py3odb

https://py3odb.readthedocs.io/en/latest/
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py3odb is a Python 3.6+ compatible interface to ECMWF’s ODB API, providing an SQL-like interface for...
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### Install py3odb using setup.py

Source: https://py3odb.readthedocs.io/en/latest/cli/index.html

Install the py3odb library from source using `setup.py`. The `--user` flag can be used for user-specific installation.

```bash
$ python3 setup.py install [--user]

```

--------------------------------

### Install py3odb using pip

Source: https://py3odb.readthedocs.io/en/latest/cli/index.html

Install the py3odb library using pip. This command makes the `_py3odb_` CLI tool available.

```bash
$ pip3 install py3odb

```

--------------------------------

### Generate Geopoints File

Source: https://py3odb.readthedocs.io/en/latest/cli/geopoints.html

Example of generating a geopoints file with a specified column and varno. The output includes metadata and data columns.

```bash
$ py3odb geopoints sample.odb -c obsvalue -v t2m
#GEO
VARNO = 39
COLUMN = obsvalue@body
  lat       lon     lvl   date      time      value
#DATA
  57.183     9.950   0   20181213   0600    272.671814
  57.100     9.850   0   20181213   0600    273.486420
  57.733    10.633   0   20181213   0600    274.932434
  56.933     8.633   0   20181213   0600    273.601471
  57.383    10.333   0   20181213   0600    273.796997
  ...


```

--------------------------------

### Generate Geopoints File with WHERE Clause

Source: https://py3odb.readthedocs.io/en/latest/cli/geopoints.html

Example of generating a geopoints file with a WHERE clause to filter data based on longitude.

```bash
$ py3odb geopoints sample.odb -c obsvalue -v t2m -w "lon > 9 AND lon < 10"
#GEO
VARNO = 39
COLUMN = obsvalue@body
  lat       lon     lvl   date      time      value
#DATA
  57.183     9.950   0   20181213   0600    272.671814
  57.100     9.850   0   20181213   0600    273.486420
  ...


```

--------------------------------

### Query Observation Data

Source: https://py3odb.readthedocs.io/en/latest/cli/query.html

Example of querying for observation data including variable number, latitude, longitude, and observed value from an ODB2 file. Shows handling of potential null values.

```bash
$ py3odb query sample.odb "SELECT varno,lat,lon,obsvalue FROM <odb>"
(162, -74.678, -35.619, 0.013708969578146935)
(241, -74.678, -35.619, None)
(7, -74.678, -35.619, None)
...

```

--------------------------------

### Query Distinct Variable Name

Source: https://py3odb.readthedocs.io/en/latest/cli/query.html

Example of querying for distinct variable names from an ODB2 file. It demonstrates using the <odb> tag to reference the filename within the SQL command.

```bash
$ py3odb query sample.odb "SELECT DISTINCT date@hdr FROM <odb>"
(20181213,)
```

--------------------------------

### Connect and Query ODB File

Source: https://py3odb.readthedocs.io/en/latest/index.html

Use this snippet to establish a connection to an ODB file and execute a SQL-like query using the py3odb module. Ensure the py3odb library is imported.

```python
import py3odb
connection = py3odb.connect('foo.db')
cursor = connection.cursor()
cursor.execute('SELECT * FROM "foo.db"')
for row in cursor:
    print(row)
connection.close()

```

--------------------------------

### Query Command Usage

Source: https://py3odb.readthedocs.io/en/latest/cli/query.html

Displays the help message for the query command, outlining its arguments and options. Use this to understand how to structure your query commands.

```bash
usage: py3odb query [-h] filename sql_command

Execute an SQL-like query against an ODB2 file.
You can replace the filename reference in the SQL command with <odb>.

Examples:
    $ py3odb query foo.odb "SELECT DISTINCT varno FROM 'foo.odb'"
    $ py3odb query foo.odb "SELECT lat,lon,obsvalue FROM <odb>"

positional arguments:
  filename     The ODB2 filename.
  sql_command  The SQL commmand to execute.  Use <odb> to reference the filename.

optional arguments:
  -h, --help   show this help message and exit


```

--------------------------------

### Read ODB File with Context Manager

Source: https://py3odb.readthedocs.io/en/latest/index.html

This snippet demonstrates using the Reader context manager for single queries on an ODB file. It simplifies resource management by automatically handling the closing of the reader.

```python
import py3odb
with py3odb.Reader('foo.db', 'SELECT * FROM <odb>') as odb_reader:
    for row in odb_reader:
        print(row)

```

--------------------------------

### Geopoints Command Usage

Source: https://py3odb.readthedocs.io/en/latest/cli/geopoints.html

Displays the usage instructions for the geopoints command, including required and optional arguments.

```bash
usage: py3odb geopoints [-h] -c COLUMN -v VARNO [-w WHERE] filename

Generate a standard 6-column geopoints file for Metview.
You must supply the filename, column, and varno.  You may use the
varno name or code.

Examples:
    $ py3odb geopoints sample.odb -c obsvalue@body -v 39
    $ py3odb geopoints sample.odb -c bgvalue -v t2m

See https://apps.ecmwf.int/odbgov/varno/

positional arguments:
  filename              The ODB2 filename.

optional arguments:
  -h, --help            show this help message and exit
  -c COLUMN, --column COLUMN
                        The column to include (e.g. obsvalue@body).
  -v VARNO, --varno VARNO
                        The varno to include.  May be either name or code.
  -w WHERE, --where WHERE
                        Adds a conditional to the SQL query.


```

--------------------------------

### Dump Command Usage

Source: https://py3odb.readthedocs.io/en/latest/cli/dump.html

Displays the help message and available arguments for the py3odb dump command. Use this to understand the command's options.

```bash
usage: py3odb dump [-h] [-c] [-v] [-vv] filename

Dump information about the ODB2 file (e.g. column names).

positional arguments:
  filename        The ODB2 filename.

optional arguments:
  -h, --help      show this help message and exit
  -c, --columns   Print the columns.
  -v, --varno     Print the varnos.
  -vv, --verbose  Print full details.

```

--------------------------------

### Dump Columns with Verbose Output

Source: https://py3odb.readthedocs.io/en/latest/cli/dump.html

Prints column names and their types from an ODB2 file with verbose details. Useful for understanding the structure of the data.

```bash
$ py3odb dump -c -vv sample.odb
---------------------------------------------------
name                                    type
---------------------------------------------------
air_quality_station_name_1@conv         TEXT
aircraft_airframe_code@conv             TEXT
aircraft_data_relay_system@conv         INTEGER
aircraft_geomagnetic_deviation@conv     FLOAT
...

```

--------------------------------

### Dump Variable Numbers with Verbose Output

Source: https://py3odb.readthedocs.io/en/latest/cli/dump.html

Prints variable numbers, their codes, and descriptions from an ODB2 file with verbose details. Useful for mapping data fields to their numerical identifiers and meanings.

```bash
$ py3odb dump --varno --verbose sample.odb
--------------------------------------------------------------------------------
name                code  description
--------------------------------------------------------------------------------
bend_angle           162  radio occultation bending angle
mean_freq            241  GPSRO mean frequency
q                      7  specific humidity (q)


```
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