'numpy.float64' object has no attribute 'translate' Inserting value to Mysql in Python

Question

import dataset
db = dataset.connect(....)
table = db[...]

When I try to insert some value into Mysql table, this error occurred.

Sample Value I am inserting to the table:

print("Buy", ticker, price, date, OType, OSize)
Buy AAPL 93.4357142857 2016-05-12 Market 200
data = dict(Order_Side='Buy',Ticker=ticker, Price=price, 
                            Order_Date= date, Order_Type = OType, Volume = OSize )
table.insert(data)

error message:

Traceback (most recent call last):

  File "<ipython-input-3-b7ab0c98f72f>", line 1, in <module>
    runfile('C:/Users/SwigelUser/Documents/GitHub/Trading/Strategies/strat_MA_ExecTest.py', wdir='C:/Users/SwigelUser/Documents/GitHub/Trading/Strategies')

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 880, in runfile
    execfile(filename, namespace)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 102, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/Users/SwigelUser/Documents/GitHub/Trading/Strategies/strat_MA_ExecTest.py", line 69, in <module>
    MA_Stra(start_length=7,end_length=10,start_date=date(2016,5,12),end_date=date(2016,6,18))

  File "C:/Users/SwigelUser/Documents/GitHub/Trading/Strategies/strat_MA_ExecTest.py", line 66, in MA_Stra
    table.insert(data1)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\dataset\persistence\table.py", line 87, in insert
    res = self.database.executable.execute(self.table.insert(row))

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\engine\base.py", line 945, in execute
    return meth(self, multiparams, params)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\sql\elements.py", line 263, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\engine\base.py", line 1053, in _execute_clauseelement
    compiled_sql, distilled_params

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\engine\base.py", line 1189, in _execute_context
    context)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\engine\base.py", line 1405, in _handle_dbapi_exception
    util.reraise(*exc_info)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\util\compat.py", line 187, in reraise
    raise value

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\engine\base.py", line 1182, in _execute_context
    context)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\sqlalchemy\engine\default.py", line 470, in do_execute
    cursor.execute(statement, parameters)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\cursors.py", line 164, in execute
    query = self.mogrify(query, args)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\cursors.py", line 143, in mogrify
    query = query % self._escape_args(args, conn)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\cursors.py", line 123, in _escape_args
    return dict((key, conn.literal(val)) for (key, val) in args.items())

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\cursors.py", line 123, in <genexpr>
    return dict((key, conn.literal(val)) for (key, val) in args.items())

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\connections.py", line 821, in literal
    return self.escape(obj, self.encoders)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\connections.py", line 814, in escape
    return escape_item(obj, self.charset, mapping=mapping)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\converters.py", line 27, in escape_item
    val = encoder(val, mapping)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\converters.py", line 110, in escape_unicode
    return u"'%s'" % _escape_unicode(value)

  File "C:\Users\SwigelUser\Anaconda3\lib\site-packages\pymysql\converters.py", line 73, in _escape_unicode
    return value.translate(_escape_table)

AttributeError: 'numpy.float64' object has no attribute 'translate'

What have caused this error? How could I solve this. It seems like I entered too much code here,thus I will have to type lots of none sense in order to submit.

my price and date variable comes from a dataframe:

for i in range(len(All_Tickers)-1-len(Current_Date),len(All_Tickers)-1):
    price = All_Tickers[str(length) + 'day_MA'][i]
    date = All_Tickers['Date'][i+1]

According to the answer below, the problem should be the type of price is np.float64, how can I convert this variable to type float?

Answer 1

Another option, that could help it is:

from sqlalchemy import event
import numpy as np
import sqlalchemy

engine = sqlalchemy.create_engine(...)

def add_own_encoders(conn, cursor, query, *args):
    cursor.connection.encoders[np.float64] = lambda value, encoders: float(value)

event.listen(engine, "before_cursor_execute", add_own_encoders)

Answer 2

Add the command below to anywhere before making pymysql connection. It adds new encoder of numpy.float64.

pymysql.converters.encoders[np.float64] = pymysql.converters.escape_float
pymysql.converters.conversions = pymysql.converters.encoders.copy()
pymysql.converters.conversions.update(pymysql.converters.decoders)

Answer 3

You can solve this problem by just adding a float method for every np.float variable like below:

variable = float(variable)

Answer 4

Your library tries to format the provided arguments to a format MySQL will understand. To do so, it checks the type of each argument, to determine how the input should be formatted.

However, since your lib doesn't knows numpy.float64, it fallbacks to a default encoder, which happens to be one for strings (unicode). Here is the relevent piece of code.

def escape_item(val, charset, mapping=None):
    if mapping is None:
        mapping = encoders
    encoder = mapping.get(type(val))

    # Fallback to default when no encoder found
    if not encoder:
        try:
            encoder = mapping[text_type]
        except KeyError:
            raise TypeError("no default type converter defined")

    if encoder in (escape_dict, escape_sequence):
        val = encoder(val, charset, mapping)
    else:
        val = encoder(val, mapping)
    return val

This encoder, assuming the input is indeed a string, tries to call the translate() method on this string. But, since this method isn't defined for float64, you get this error.

You should try to convert your float64 to a regular float.

Or, you can create your own encoder, and add it in the encoders dict used as the default mapping of python types to encoder. If you're going to use a lot this lib with float64, it may be worth doing.