Save callbacks

simple.py

##############################################
#
# Filter & modify
#
# ------------------------------
# Callback
def callback(cube, field, filename)
    if field.bar > 3:
        raise iris.exceptions.IgnoreFieldException
    field.foo = 9
iris.save(cubes, 'stuff.grib2', callback=callback)
# ------------------------------
# Eager evaluation
messages = []
for message in iris.fileformats.grib.as_messages(cubes):
    if message.bar > 3:
        continue
    message.foo = 9
    messages.append(message)
iris.fileformats.grib.save(messages, 'stuff.grib2')
# ------------------------------
# Lazy evaluation (generator expression)
def modify(message):
    message.foo = 9
    return message
messages = iris.fileformats.grib.as_messages(cubes)
messages = (modify(message) for message in messages if message.bar > 3)
iris.fileformats.grib.save(messages, 'stuff.grib2')
# ------------------------------
# Lazy evaluation (generator function)
def lazy(cubes):
    for message in iris.fileformats.grib.as_messages(cubes)
        if message.bar > 3:
            continue
        message.foo = 9
        yield message
iris.fileformats.grib.save(lazy(cubes), 'stuff.grib2')

use_cube.py

##############################################
#
# Filter & modify using corresponding cube
#
# ------------------------------
# Callback
def callback(cube, field, filename)
    if field.bar > 3:
        raise iris.exceptions.IgnoreFieldException
    field.foo = cube.attributes['foo']
iris.save(cubes, 'stuff.grib2', callback=callback)
# ------------------------------
# Eager evaluation
messages = []
for cube in cubes:
    for message in iris.fileformats.grib.as_messages(cubes):
        if message.bar > 3:
            continue
        message.foo = cube.attributes['foo']
        messages.append(message)
iris.fileformats.grib.save(messages, 'stuff.grib2')
# ------------------------------
# Lazy evaluation (generator function)
def lazy(cubes):
    for cube in cubes:
        for message in iris.fileformats.grib.as_messages(cubes):
            if message.bar > 3:
                continue
            message.foo = cube.attributes['foo']
            yield message
iris.fileformats.grib.save(lazy(cubes), 'stuff.grib2')