Pandas To_datetime Valueerror: Unknown String Format

I have a column in my (pandas) dataframe: data['Start Date'].head() type(data['Start Date']) Output: 1/7/13 1/7/13 1/7/13 16/7/13 16/7/13

Solution 1:

I think the problem is in data - a problematic string exists. So you can try check length of the string in column Start Date:

import pandas as pd
import io

temp=u"""Start Date
1/7/13
1/7/1
1/7/13 12 17
16/7/13
16/7/13"""

data = pd.read_csv(io.StringIO(temp), sep=";", parse_dates=False)

#data['Start Date']= pd.to_datetime(data['Start Date'],dayfirst=True)print data

     Start Date
01/7/1311/7/121/7/131217316/7/13416/7/13#check, if length is more as 7print data[data['Start Date'].str.len() > 7]

     Start Date
21/7/131217

Or you can try to find these problematic row different way e.g. read only part of the datetime and check parsing datetime:

#read first 3 rows
data= data.iloc[:3]

data['Start Date']= pd.to_datetime(data['Start Date'],dayfirst=True)

But this is only tips.

EDIT:

Thanks joris for suggestion add parameter errors ='coerce' to to_datetime:

temp=u"""Start Date
1/7/13
1/7/1
1/7/13 12 17
16/7/13
16/7/13 12 04"""

data = pd.read_csv(io.StringIO(temp), sep=";")
#add parameter errors coerce
data['Start Date']= pd.to_datetime(data['Start Date'], dayfirst=True, errors='coerce')
print data

  Start Date
02013-07-01
12001-07-01
2        NaT
32013-07-164        NaT

#index of data with null - NaT to variable idx
idx = data[data['Start Date'].isnull()].index
print idx

Int64Index([2, 4], dtype='int64')

#read csv again
data = pd.read_csv(io.StringIO(temp), sep=";")

#find problematic rows, where datetime is not parsedprint data.iloc[idx]

      Start Date
21/7/131217416/7/1312 04