AttributeError list object has no attribute add

Question

Python is new for me and I am doing some machine learning code using python. My scenario is that I am reading data from my sql and trying to give a shape to this data so i can use it for MLP training.

My code is below:

connection = mysql.connector.connect(host='localhost', port=3306, user='root', passwd='mysql', db='medicalgame')

cur = connection.cursor()
query = ""
cur.execute(query)
# X_train will be a list of list and later we'll convert it to a numpy ndarray
X_train = []

for row in cur:
    X_train.add(row)
connection.close()

X_train should be ready
X_train = np.asarray(X_train)
print 'The shape of X_train is', X_train.shape

During debug the query result i got is like this: (6, 1, 1, 1, 2, u'F', 1, 0, 0, 19) Can anyone help me how can, I fix the error and give shape to my X_train, so that MLP accept it as an input ?

Answer 1

the message is clear. list has no method add because it is ordered (it has a dunder __add__ method but that's for addition between lists). You can insert but you want to append. So the correct way is:

X_train = []

for row in cur:
    X_train.append(row)

BUT the preferred way converting to a list directly (iterating on cur elements to create your list in a simple and performant way):

X_train = list(cur)

BUT you cannot do that since your list contains bogus data. Fortunately, you can filter them out in a nested list comprehension like this:

X_train = [[x for x in r if type(x)==int] for r in cur]

this builds your list of lists but filters out non-integer values and feeding it to numpy.asarray yields (with your sample data):

[[ 6  1  1  1  2  1  0  0 19]
 [ 6  1  1  1  2  1  0  0 14]]