README.md

snapista – a frictionless Python wrapper for SNAP GPT

This version of snapista is my personal take on what is originally presented here.

What's different

• In my vision, the central object of the package is not the graph, but gpt itself.
• The snapista.GPT object is initiated with a path to gpt to avoid any confusions with system's PATH.
  
• There is no dependence on snappy. Instead, the operators are manually defined through the snapista.operators package.
• The descriptions for operators are included into the docstrings, so they are accessible via help(operator) or operator? in interactive environments.
• The parameters are set by setting the corresponding operator's properties, and they are in Python types (the booleans are True and False instead of 'true' and 'false' and lists are actual Python lists).
• snapista.GPT.run method is very flexible in terms of output formatting.

Below is an example of one of my personal workflows that I also used for testing.

import os
import pathlib
import snapista

gpt_path = pathlib.Path('~/.esa-snap/bin/gpt').expanduser()

data = pathlib.Path('Data') / 'raw' / 'MSI'
products = [data / f for f in os.listdir(data) if 'S2' in f]

gpt = snapista.GPT(gpt_path)

resample = snapista.operators.Resample()
resample.reference_band = 'B2'

import_vector = snapista.operators.ImportVector()
import_vector.separate_shapes = False
import_vector.vector_file = '/home/greg/Vectors/Land.shp'

land_sea_mask = snapista.operators.LandSeaMask()
land_sea_mask.use_srtm = False
land_sea_mask.geometry = 'Land'
land_sea_mask.invert_geometry = True

graph = snapista.Graph()
graph.add_node(resample)
graph.add_node(import_vector)
graph.add_node(land_sea_mask)

gpt.run(
    graph,
    products,
    output_folder='Data/proc',
    format_='BEAM-DIMAP',
    date_time_only=True,
    prefix='S2_',
    suppress_stderr=True,
)

Installation

I don't have an installation option yet. I will look into uploading it to PyPI as soon as I come with a cool name that makes it clear that is not the original snapista. To run tests, I manually insert the path to the local repository into Python's sys.path.

import sys
import pathlib

snapista_path = pathlib.Path('~/Projects/snapista/').expanduser()

if str(snapista_path) not in sys.path:
    sys.path.insert(0, str(snapista_path))

import snapista