Convert pandas dataframe column containing Excel general numbers into datetime object - excel

Question

I have a dataframe that I constructed from pulling data from SQL using pd.read_sql_query(). I have one column that has dates but in excel general number format. How do convert this column into datetime object.
I can convert one value with the xlrd library but looking for the best way to convert the entire column.
datetime_value = datetime(*xlrd.xldate_as_tuple(42369, 0))

Answer 1

You can use map to apply a lambda function performing that operation to every entry in a column:
import pandas as pd
import xlrd
from datetime import datetime
# Create dummy dataframe
df = pd.DataFrame({
"date": [42369, 42370, 42371, 42372]
})
print df.to_string()
# Convert values into a new column named "converted"
df["converted"] = df["date"].map(lambda x: datetime(*xlrd.xldate_as_tuple(x, 0)))
print df.to_string()
Before conversion:
date
0 42369
1 42370
2 42371
3 42372
After:
date converted
0 42369 2015-12-31
1 42370 2016-01-01
2 42371 2016-01-02
3 42372 2016-01-03
Is this what you are looking for?
Update:
To make this work with string entries, you could either tell Pandas to treat the column as ints or floats:
# int
df["converted"] = df["date"].astype(int).map(lambda x: datetime(*xlrd.xldate_as_tuple(x, 0)))
# float
df["converted"] = df["date"].astype(float).map(lambda x: datetime(*xlrd.xldate_as_tuple(x, 0)))
or just cast x to int or float within the lambda function:
# int
df["converted"] = df["date"].map(lambda x: datetime(*xlrd.xldate_as_tuple(int(x), 0)))
# float
df["converted"] = df["date"].map(lambda x: datetime(*xlrd.xldate_as_tuple(float(x), 0)))