Python strftime days without ZERO

Question

Why doesn't the codes from this page work?: http://strftime.org/. I want to output date and months without leading zeroes, like 'm/d/yyyy'

e.g.: '4/5/1992' YES

'04/05/1992' NO

from datetime import datetime, timedelta, date
yest = datetime.strftime(datetime.now() - timedelta(21), '%-m-%-d-%Y')
print(yest)

ValueError Traceback (most recent call last)
<ipython-input-35-7c70a0a7eee5> in <module>
 1 from datetime import datetime, timedelta, date
----> 2 yest = datetime.strftime(datetime.now() - timedelta(21), '%-m-%-d-%Y')
 3 print(yest)
ValueError: Invalid format string

Answer 1

That %-m option does state that the format is platform specific, so mileage may vary.

You can simply use f-strings in Python 3.

yest = datetime.now() - timedelta(21)
yest = f'{yest.month}/{yest.day}/{yest.year}'
>>> yest
'10/9/2019'

In the case of your dataframe explained in the comments:

df = pd.DataFrame({
 'fecha_vencimiento': [
 '12/25/2009', '01/05/2010', '04/13/2011', '']})
df['fecha_vencimiento'] = pd.to_datetime(
 df['fecha_vencimiento'], format='%m/%d/%Y', errors='coerce').apply(
 lambda x: f'{x.month}/{x.day}/{x.year}' 
 if pd.notnull(x) else '')

• salem1992: thanks!! for example i have this column of dates, but give me error: f'{df.at[idx,'fecha_vencimiento'].month}/{df.at[idx,'fecha_vencimiento'].day}/{df.at[idx,'fecha_vencimiento'].year}
• Alexander: Try using the dt accessor function, f'{df.at[idx,'fecha_vencimiento'].dt.month}/{df.at[idx,'fecha_vencimiento'].dt.day}/{df.at[idx,'fecha_vencimiento'].dt.year}'
• salem1992: give me SyntaxError: invalid syntax :(
• salem1992: df.at[idx,'fecha_vencimiento'] = f'{df.at[idx,'fecha_vencimiento'].dt.month}/{df.at[idx,'fecha_vencimiento'].dt.day}/{df.at[idx,'fecha_vencimiento'].dt.year}'
• Alexander: What is the output of type(df.at[idx,'fecha_vencimiento'])? That is, what do the date values currently look like? Strings, datetime values, timestamps, etc.

Answer 2

The %-d would give you the day without the leading 0 and %-m the month, but this format only works on Unix (Linux, OS X), not Windows (including Cygwin). On Windows, you would use #, e.g. %#d, %#m.