Reuven M. Lerner

#Python methods are stored on a class, not an instance.

Given x.m(), how does Python find it?

The ICPO rule:

- First, look for an attribute on the _i_nstance.
- Not there? Look on the _c_lass.
- Not here? Look on the _p_arent.
- Not there? Look on _o_bject, the final parent.

I just finished giving my talk at the #PyConUS education summit, "Vibe teaching: #Python training in the age of AI."

What fun!

I've uploaded the slides: https://speakerdeck.com/reuven/vibe-teaching-python-training-in-the-age-of-ai-pycon-us-2026-education-summit

By default, every #Python class inherits from "object".

You can see this by checking the __bases__ attribute on a class:

class C:
pass

print(C.__bases__) # prints (<class 'object'>,)

__bases__ is a tuple — hinting (correctly) that Python supports multiple inheritance.

It's time for #PyConUS! We're in Long Beach, California, near one of the most active ports in the world.

As such, Bamboo Weekly's challenges are about the Port of Long Beach — how much traffic it gets, what is imported, and from where.

Level up your #Python and #Pandas: https://BambooWeekly.com

How free is the press in your country? Challenge your #Python #Pandas skills — merging files, pivot tables, and plots — on the most recent data from Reporters Without Borders.

Don't settle for toy data sets. Level up with real data and real challenges with Bamboo Weekly.

Learn more at https://BambooWeekly.com

The Strait of Hormuz remains closed. And US gas prices continue to rise.

Bamboo Weekly challenges you to use #Python #Pandas to find where they're highest, how much they've increased — plus create interactive maps.

Level up your data skills every Wednesday!

Check it out: https://BambooWeekly.com

Want to round #Python #Pandas datetimes? You have 3 options:

- dt.floor — earlier
- dt.ceil - later
- dt.round — nearest

For example:

s.dt.floor('3h') # previous multiple-of-3 hour
s.dt.ceil('15m') # next 15-minute block
s.dt.round('1D') # nearest 1 day

Want to set the time on a #Python #Pandas series of datetimes to midnight? Use dt.normalize:

df['x'].dt.normalize()

You get back series of datetime values, but all times are 00:00:00.

Want to convert a #Python #Pandas datetime column to Unix time (seconds since 1970)?

df['date'].astype('int64')

That's it! No division needed.

The Strait of Hormuz is still closed, and oil prices remain high.

But which are higher, spot prices or oil futures?

In the latest Bamboo Weekly, I give you six #Python #Pandas data-analysis problems to solve about oil prices using public data.

More info: https://BambooWeekly.com

Want to convert an integer #Python #Pandas column from Unix time to datetime?

Use pd.to_datetime, passing the int column and the "unit" keyword argument, set to "s" (seconds):

df['date'] = pd.to_datetime(df['unixtime'],unit='s')

If the column is in ms, then say unit='ms'

Want to check if two #Python #Pandas datetimes are in the same month/quarter/year?

Convert them both to periods, and compare with ==:

date1.to_period('M') == date2.to_period('M') # same month?
date1.to_period('Q') == date2.to_period('Q') # same quarter?

Want to find which time period contains a #Python #Pandas datetime? Use to_period:

pd.Timestamp.now().to_period('1D')
pd.Timestamp.now().to_period('6W')

This returns a Pandas "Period" object, useful (among other things) for checking if two dates are within the same period.

Want to find leap years in a #Python #Pandas datetime series? Use dt.is_leap_year:

df = DataFrame({'x':np.arange(32),
'y': pd.date_range(start='1995-04-19',
end='2027-04-19', freq='1YE')})

df.loc[pd.col('y').dt.is_leap_year] # returns boolean series

Want to know if values in a #Python #Pandas datetime series are at the start/end of a period? Get a boolean series from:

df['x'].dt.is_month_start # or dt.is_month_end
df['x'].dt.is_quarter_start # or dt.is_quarter_end
df['x'].dt.is_year_start # or dt.is_year_end

Use dt.day_of_week to get the day number from a #Python #Pandas datetime series.

But is 0 Sunday or Monday? Or not used at all?

Better: Use the day_name method:

df['x'].dt.day_name()

Good news: It returns a series of strings!
Bad news: It's 4x slower.

Do Americans pay more taxes than in other countries? Do they pay more in income taxes?

Explore OECD data with #Python, #Pandas, Marimo, and Claude Code (plus the new marimo-pair skill) in the latest Bamboo Weekly, and find out!

Read all about it: https://BambooWeekly.com

Want to grab a part of datetime value in a #Python #Pandas data frame column? Use "dt":

df['x'].dt.year
df['x'].dt.hour
df['x'].dt.minute
df['x'].dt.day_of_week # or dayofweek or weekday

day_of_week returns an integer, where 0 is Monday and 6 is Sunday.

It's tax day in the US — and according to Gallup, Americans think taxes are too high. But... how high are they vs. other countries?

In the latest Bamboo Weekly, I pose 6 questions about taxes. Can you solve them with marimo-pair, Marimo, Claude Code, and #Python #Pandas?

Check it out: https://BambooWeekly.com

Reading a CSV into #Python #Pandas, and parse_dates doesn't recognize the format? Pass the date_format keyword arg:

df = pd.read_csv(filename,
parse_dates=['x', 'y'],
date_format='%Y-%m-%d %H:%M:%S')

All strftime codes work!

Reading a CSV into #Python #Pandas, and want a column to be treated as datetime values? Use parse_dates:

df = pd.read_csv(filename,
parse_dates=['x', 'y'])

Bonus: The PyArrow engine often (not always) parses columns that look like dates.

Want to take a #Python #Pandas series of strings, and get datetime values? Use pd.to_datetime:

pd.to_datetime(df['x'])

Notice: It's not a method! It's a top-level pd function.

Specify a non-standard "format" with a strftime string:

pd.to_datetime(df['x'], format='%d/%m/%Y')

Happy 3rd anniversary, Bamboo Weekly!

This is issue 156, marking 3 years of weekly Pandas challenges.

This week, we look at Winter Olympic data. Since they love snow so much, we'll use #Polars along with #Python #Pandas.

Check it out, at https://BambooWeekly.com.