1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
|
from collections import OrderedDict
from agate.exceptions import DataTypeError
from agate.rows import Row
@classmethod
def merge(cls, tables, row_names=None, column_names=None):
"""
Create a new table from a sequence of similar tables.
This method will not carry over row names from the merged tables, but new
row names can be specified with the :code:`row_names` argument.
It is possible to limit the columns included in the new :class:`.Table`
with :code:`column_names` argument. For example, to only include columns
from a specific table, set :code:`column_names` equal to
:code:`table.column_names`.
:param tables:
An sequence of :class:`.Table` instances.
:param row_names:
See :class:`.Table` for the usage of this parameter.
:param column_names:
A sequence of column names to include in the new :class:`.Table`. If
not specified, all distinct column names from `tables` are included.
:returns:
A new :class:`.Table`.
"""
from agate.table import Table
new_columns = OrderedDict()
for table in tables:
for i in range(0, len(table.columns)):
if column_names is None or table.column_names[i] in column_names:
column_name = table.column_names[i]
column_type = table.column_types[i]
if column_name in new_columns:
if not isinstance(column_type, type(new_columns[column_name])):
raise DataTypeError('Tables contain columns with the same names, but different types.')
else:
new_columns[column_name] = column_type
column_keys = tuple(new_columns.keys())
column_types = tuple(new_columns.values())
rows = []
for table in tables:
# Performance optimization for identical table structures
if table.column_names == column_keys and table.column_types == column_types:
rows.extend(table.rows)
else:
for row in table.rows:
data = []
for column_key in column_keys:
data.append(row.get(column_key, None))
rows.append(Row(data, column_keys))
return Table(rows, column_keys, column_types, row_names=row_names, _is_fork=True)
|
