Select columns based on dates - Pandas

[Richard Medina]

On Friday, September 3, 2021 at 11:57:12 AM UTC-5, Martin Di Paola wrote:
> You may want to reshape the dataset to a tidy format: Pandas works 
> better with that format. 
> 
> Let's assume the following dataset (this is what I understood from your 
> message): 
> 
> In [34]: df = pd.DataFrame({ 
> ...: 'Country': ['us', 'uk', 'it'], 
> ...: '01/01/2019': [10, 20, 30], 
> ...: '02/01/2019': [12, 22, 32], 
> ...: '03/01/2019': [14, 24, 34], 
> ...: }) 
> 
> In [35]: df 
> Out[35]: 
> Country 01/01/2019 02/01/2019 03/01/2019 
> 0 us 10 12 14 
> 1 uk 20 22 24 
> 2 it 30 32 34 
> 
> Then, reshape it to a tidy format. Notice how each row now represents 
> a single measure. 
> 
> In [43]: pd.melt(df, id_vars=['Country'], var_name='Date', 
> value_name='Cases') 
> Out[43]: 
> Country Date Cases 
> 0 us 01/01/2019 10 
> 1 uk 01/01/2019 20 
> 2 it 01/01/2019 30 
> 3 us 02/01/2019 12 
> 4 uk 02/01/2019 22 
> 5 it 02/01/2019 32 
> 6 us 03/01/2019 14 
> 7 uk 03/01/2019 24 
> 8 it 03/01/2019 34 
> 
> I used strings to represent the dates but it is much handy work 
> with real date objects. 
> 
> In [44]: df2 = _ 
> In [45]: df2['Date'] = pd.to_datetime(df2['Date']) 
> 
> Now we can filter by date: 
> 
> In [50]: df2[df2['Date'] < '2019-03-01'] 
> Out[50]: 
> Country Date Cases 
> 0 us 2019-01-01 10 
> 1 uk 2019-01-01 20 
> 2 it 2019-01-01 30 
> 3 us 2019-02-01 12 
> 4 uk 2019-02-01 22 
> 5 it 2019-02-01 32 
> 
> With that you could create three dataframes, one per month. 
> 
> Thanks, 
> Martin.
> On Thu, Sep 02, 2021 at 12:28:31PM -0700, Richard Medina wrote: 
> >Hello, forum, 
> >I have a data frame with covid-19 cases per month from 2019 - 2021 like a header like this: 
> > 
> >Country, 01/01/2019, 2/01/2019, 01/02/2019, 3/01/2019, ... 01/01/2021, 2/01/2021, 01/02/2021, 3/01/2021 
> > 
> >I want to filter my data frame for columns of a specific month range of march to September of 2019, 2020, and 2021 only (three data frames). 
> > 
> >Any ideas? 
> >Thank you 
> > 
> >
> >-- 
> >https://mail.python.org/mailman/listinfo/python-list
Thank you, Martin,
Is it possible to select/filter the dates (like columns from a date range) from the columns without reshaping them?
Thank you for your answer.