Add SQLHelpers.

SQLHelpers/sqlhelpers.py

@@ -0,0 +1,67 @@
+def insert_filler(column_names, values, require_all=True):
+    '''
+    Manually aligning the bindings for INSERT statements is annoying.
+    Given the table's column names and a dictionary of {column: value},
+    return the question marks and the list of bindings in the right order.
+
+    require_all:
+        If `values` does not contain one of the column names, should we raise
+        an exception?
+        Otherwise, that column will simply receive None.
+
+    Example:
+    column_names=['id', 'name', 'score'],
+    values={'score': 20, 'id': '1111', 'name': 'James'}
+    ->
+    returns ('?, ?, ?', ['1111', 'James', 20])
+
+    In context:
+    (qmarks, bindings) = insert_filler(COLUMN_NAMES, data)
+    query = 'INSERT INTO table VALUES(%s)' % qmarks
+    cur.execute(query, bindings)
+    '''
+    values = values.copy()
+    for column in column_names:
+        if column in values:
+            continue
+        if require_all:
+            raise ValueError('Missing column "%s"' % column)
+        else:
+            values[column] = None
+    qmarks = '?' * len(column_names)
+    qmarks = ', '.join(qmarks)
+    bindings = [values[column] for column in column_names]
+    return (qmarks, bindings)
+
+def update_filler(pairs, where_key):
+    '''
+    Manually aligning the bindings for UPDATE statements is annoying.
+    Given a dictionary of {column: value} as well as the name of the column
+    to be used as the WHERE, return the "SET ..." portion of the query and the
+    bindings in the correct order.
+
+    Example:
+    pairs={'id': '1111', 'name': 'James', 'score': 20},
+    where_key='id'
+    ->
+    returns ('SET name = ?, score = ? WHERE id == ?', ['James', 20, '1111'])
+
+    In context:
+    (query, bindings) = update_filler(data, where_key)
+    query = 'UPDATE table %s' % query
+    cur.execute(query, bindings)
+    '''
+    pairs = pairs.copy()
+    where_value = pairs.pop(where_key)
+    if len(pairs) == 0:
+        raise ValueError('No pairs left after where_key.')
+    qmarks = []
+    bindings = []
+    for (key, value) in pairs.items():
+        qmarks.append('%s = ?' % key)
+        bindings.append(value)
+    bindings.append(where_value)
+    qmarks = ', '.join(qmarks)
+    query = 'SET {setters} WHERE {where_key} == ?'
+    query = query.format(setters=qmarks, where_key=where_key)
+    return (query, bindings)