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#
# Copyright 2011 Twitter, Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Example illustrating the different types of map operations.
In the output folders check the .pycascading_types and .pycascading_header
files to see what the names of the fields were when the pipes were sinked.
"""
from pycascading.helpers import *
def main():
flow = Flow()
input = flow.source(Hfs(TextLine(), 'pycascading_data/town.txt'))
out_folder = 'pycascading_data/maps/'
@udf(produces='word')
def decorated_udf(tuple):
for word in tuple.get('line').split():
yield [word]
def undecorated_udf(tuple):
for word in tuple.get('line').split():
yield [word]
# This will create an output with one field called 'word', as the UDF
# was declared with a 'produces'
# In this case the swap swaps out the whole input tuple with the output
input | map_replace(decorated_udf) | \
flow.tsv_sink(out_folder + 'decorated_udf')
# This will create an output with one unnamed field, but otherwise the
# same as the previous one
input | map_replace(undecorated_udf) | \
flow.tsv_sink(out_folder + 'undecorated_udf')
# This will only replace the first ('line') field with the output of
# the map, but 'offset' will be retained
# Note that once we add an unnamed field, all field names will be lost
input | map_replace(1, undecorated_udf) | \
flow.tsv_sink(out_folder + 'undecorated_udf_with_input_args')
# This will create one field only, 'word', just like the first example
input | map_replace(undecorated_udf, 'word') | \
flow.tsv_sink(out_folder + 'undecorated_udf_with_output_fields')
# This one will add the new column, 'word', to all lines
input | map_add(decorated_udf) | \
flow.tsv_sink(out_folder + 'decorated_udf_all')
# This produces the same output as the previous example
input | map_add(1, undecorated_udf, 'word') | \
flow.tsv_sink(out_folder + 'undecorated_udf_all')
flow.run(num_reducers=1)