无法将字符串转换为浮点数 Python - Pandas DataFrames

Question

Hi I am getting this error but everything seems ok.

import matplotlib.pyplot as mpl
import pandas as pd

#Uploading data to Python Pandas Dataframe

db_fondos = pd.read_excel('/Users/jonathanprieto/Documents/GitHub/GoogleMaps/data/- Matriz TDF Python.xlsm',
                       sheet_name="DB Fondos")
ts_flujos = pd.read_excel('/Users/jonathanprieto/Documents/GitHub/GoogleMaps/data/- Matriz TDF Python.xlsm',
                       sheet_name="TS Flujos")
ts_ind_fin = pd.read_excel('/Users/jonathanprieto/Documents/GitHub/GoogleMaps/data/- Matriz TDF Python.xlsm',
                       sheet_name="TS Ind. Fin.")
ts_market = pd.read_excel('/Users/jonathanprieto/Documents/GitHub/GoogleMaps/data/- Matriz TDF Python.xlsm',
                       sheet_name="TS Market data")
db_posiciones = pd.read_excel('/Users/jonathanprieto/Documents/GitHub/GoogleMaps/data/- Matriz TDF Python.xlsm',
                       sheet_name="DB Posiciones")
print('Carga completada')


#NaN = np.nan
#db_posiciones["Id. Pos."] = NaN
#db_posiciones.head()

print(db_posiciones)

diccionario=db_fondos.set_index("Fondo")["Id. Fondo"].to_dict()

for index, row in db_posiciones.iterrows():
    ipos = row["Fondo"]
    print(ipos)
    if ipos in diccionario:
        idpos=diccionario[ipos]
        twofirst=row["Fondo"][:2]
        twofirst = twofirst[0:2]
        print(idpos+"-"+twofirst)
        db_posiciones["Id. Pos."].values[index] = str(idpos)+"-"+str(twofirst)
        print(index)
print(db_posiciones)

Could anyone told me why I am getting this error:

File "/Users/jonathanprieto/Documents/GitHub/GoogleMaps/test.py", line 36, in <module>
db_posiciones["Id. Pos."].values[index] = str(idpos) + "-" + str(twofirst)

ValueError: could not convert string to float: '91_AGSACB_08-65'

Answer 1

You're getting this because your series is string, but it contains some NAs, which actually get represented in pandas as nan , which is a float value (that's how pd.read_csv() will handle it). That's why pandas gives a strange warning claiming the string series is a float:

Solution: first, fill any NA values in your string column with empty-string:

df[column].fillna('', inplace=True)

Notes:

• make sure to use fillna(..., inplace=True) so you don't need to assign the result back to df['column'] to prevent it getting thrown away.
• for doc, see pd.Series.fillna(..., inplace=True)
• you can fill several Series (/columns) in your dataframe at once, with df.fillna rather than df[column].fillna(..., inplace=True) on each column. See pd.DataFrame.fillna()

Answer 2

df[column] = df[column].apply(lambda x: float(x.split()[0].replace(',', '')))