forked from wireservice/csvkit
/
join.py
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join.py
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#!/usr/bin/env python
def _get_ordered_keys(rows, column_index):
"""
Get ordered keys from rows, given the key column index.
"""
return [r[column_index] for r in rows]
def _get_mapped_keys(rows, column_index):
mapped_keys = {}
for r in rows:
key = r[column_index]
if key in mapped_keys:
mapped_keys[key].append(r)
else:
mapped_keys[key] = [r]
return mapped_keys
def sequential_join(left_table, right_table):
"""
Join two tables by aligning them horizontally without performing any filtering.
"""
# Grab headers
left_headers = left_table[0]
right_headers = right_table[0]
left_rows = left_table[1:]
right_rows = iter(right_table[1:])
output = [left_headers + right_headers]
for left_row in left_rows:
try:
right_row = next(right_rows)
except StopIteration:
output.append(left_row + ([u''] * len(right_headers)))
output.append(left_row + right_row)
for right_row in right_rows:
output.append(([u''] * len(left_headers)) + right_row)
return output
def inner_join(left_table, left_column_id, right_table, right_column_id):
"""
Execute an inner join on two tables and return the combined table.
"""
# Grab headers
left_headers = left_table[0]
right_headers = right_table[0]
left_rows = left_table[1:]
right_rows = right_table[1:]
# Map right rows to keys
right_mapped_keys = _get_mapped_keys(right_rows, right_column_id)
output = [left_headers + right_headers]
for left_row in left_rows:
left_key = left_row[left_column_id]
if left_key in right_mapped_keys:
for right_row in right_mapped_keys[left_key]:
output.append(left_row + right_row)
return output
def full_outer_join(left_table, left_column_id, right_table, right_column_id):
"""
Execute full outer join on two tables and return the combined table.
"""
# Grab headers
left_headers = left_table[0]
right_headers = right_table[0]
left_rows = left_table[1:]
right_rows = right_table[1:]
# Get ordered keys
left_ordered_keys = _get_ordered_keys(left_rows, left_column_id)
# Get mapped keys
right_mapped_keys = _get_mapped_keys(right_rows, right_column_id)
output = [left_headers + right_headers]
for left_row in left_rows:
left_key = left_row[left_column_id]
if left_key in right_mapped_keys:
for right_row in right_mapped_keys[left_key]:
output.append(left_row + right_row)
else:
output.append(left_row + ([u''] * len(right_headers)))
for right_row in right_rows:
right_key = right_row[right_column_id]
if right_key not in left_ordered_keys:
output.append(([u''] * len(left_headers)) + right_row)
return output
def left_outer_join(left_table, left_column_id, right_table, right_column_id):
"""
Execute left outer join on two tables and return the combined table.
"""
# Grab headers
left_headers = left_table[0]
right_headers = right_table[0]
left_rows = left_table[1:]
right_rows = right_table[1:]
# Get mapped keys
right_mapped_keys = _get_mapped_keys(right_rows, right_column_id)
output = [left_headers + right_headers]
for left_row in left_rows:
left_key = left_row[left_column_id]
if left_key in right_mapped_keys:
for right_row in right_mapped_keys[left_key]:
output.append(left_row + right_row)
else:
output.append(left_row + ([u''] * len(right_headers)))
return output
def right_outer_join(left_table, left_column_id, right_table, right_column_id):
"""
Execute right outer join on two tables and return the combined table.
"""
# Grab headers
left_headers = left_table[0]
right_headers = right_table[0]
left_rows = left_table[1:]
right_rows = right_table[1:]
# Get ordered keys
left_ordered_keys = _get_ordered_keys(left_rows, left_column_id)
# Get mapped keys
right_mapped_keys = _get_mapped_keys(right_rows, right_column_id)
output = [left_headers + right_headers]
for left_row in left_rows:
left_key = left_row[left_column_id]
if left_key in right_mapped_keys:
for right_row in right_mapped_keys[left_key]:
output.append(left_row + right_row)
for right_row in right_rows:
right_key = right_row[right_column_id]
if right_key not in left_ordered_keys:
output.append(([u''] * len(left_headers)) + right_row)
return output