Created
April 14, 2013 19:56
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A slightly modified version of Pandas SQL DataFrame read which accepts an SQLAlchemy Engine object instead of a DBAPI connection object.
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""" | |
Collection of query wrappers / abstractions to both facilitate data | |
retrieval and to reduce dependency on DB-specific API. | |
""" | |
from pandas.core.api import DataFrame | |
def _safe_fetch(cur): | |
try: | |
result = cur.fetchall() | |
if not isinstance(result, list): | |
result = list(result) | |
return result | |
except Exception as e: # pragma: no cover | |
excName = e.__class__.__name__ | |
if excName == 'OperationalError': | |
return [] | |
def read_frame(sql, eng, index_col=None, coerce_float=True): | |
""" | |
Returns a DataFrame corresponding to the result set of the query | |
string. | |
Optionally provide an index_col parameter to use one of the | |
columns as the index. Otherwise will be 0 to len(results) - 1. | |
Parameters | |
---------- | |
sql: string | |
SQL query to be executed | |
eng: sqlalchemy engine | |
index_col: string, optional | |
column name to use for the returned DataFrame object. | |
""" | |
cur = eng.execute(sql) | |
rows = _safe_fetch(cur) | |
columns = cur.keys() | |
cur.close() | |
result = DataFrame.from_records(rows, columns=columns, | |
coerce_float=coerce_float) | |
if index_col is not None: | |
result = result.set_index(index_col) | |
return result | |
frame_query = read_frame |
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