Reuven M. Lerner
@lernerpython.com
Helping you become more confident with Python and Pandas since 1995.
• Courses: LernerPython.com
• Newsletters: BetterDevelopersWeekly.com • BambooWeekly.com
• Books: PythonWorkout.com • PandasWorkout.com
• Videos: YouTube.com/reuvenlerner
• Courses: LernerPython.com
• Newsletters: BetterDevelopersWeekly.com • BambooWeekly.com
• Books: PythonWorkout.com • PandasWorkout.com
• Videos: YouTube.com/reuvenlerner
Pinned
Reuven M. Lerner
@lernerpython.com
· Nov 12
Hi there! 👋 I'm Reuven, and I've been teaching #Python and Pandas around the world since 1995.
Just about every day, my students ask great questions. I love sharing those questions (and my answers), along with other resources to help you improve your Python/Pandas fluency.
Just about every day, my students ask great questions. I love sharing those questions (and my answers), along with other resources to help you improve your Python/Pandas fluency.
What proportion of Kalshi's contracts are about sports?
In the latest Bamboo Weekly, we use #Pandas to look into this popular prediction market, calculating the number of contracts in each category and then plotting them.
Get real-world Pandas practice every Wednesday: bambooweekly.com
In the latest Bamboo Weekly, we use #Pandas to look into this popular prediction market, calculating the number of contracts in each category and then plotting them.
Get real-world Pandas practice every Wednesday: bambooweekly.com
December 25, 2025 at 4:15 PM
What proportion of Kalshi's contracts are about sports?
In the latest Bamboo Weekly, we use #Pandas to look into this popular prediction market, calculating the number of contracts in each category and then plotting them.
Get real-world Pandas practice every Wednesday: bambooweekly.com
In the latest Bamboo Weekly, we use #Pandas to look into this popular prediction market, calculating the number of contracts in each category and then plotting them.
Get real-world Pandas practice every Wednesday: bambooweekly.com
Do you use categories in Pandas? And do you use groupby?
#Pandas 3 will change the default behavior, from observed=False to observed=True.
In my latest video, I explain what this means, and what you'll need to do when upgrading: youtu.be/bmf7crcJm9k
#Pandas 3 will change the default behavior, from observed=False to observed=True.
In my latest video, I explain what this means, and what you'll need to do when upgrading: youtu.be/bmf7crcJm9k
Pandas 3's groupby defaults to observed=True? What does that mean?
If you use groupby and categorical columns, you might have seen warnings about observed=False no longer being the default in Pandas 3. In this video, I explain why you would want to use categoricals,…
youtu.be
December 25, 2025 at 3:46 PM
Do you use categories in Pandas? And do you use groupby?
#Pandas 3 will change the default behavior, from observed=False to observed=True.
In my latest video, I explain what this means, and what you'll need to do when upgrading: youtu.be/bmf7crcJm9k
#Pandas 3 will change the default behavior, from observed=False to observed=True.
In my latest video, I explain what this means, and what you'll need to do when upgrading: youtu.be/bmf7crcJm9k
How much of the Kalshi prediction market's contracts are about sports? And did court rulings last October help their business?
In the latest Bamboo Weekly, we use Pandas to analyze data about Kalshi's markets.
Level up your data-analysis skills every Wednesday: bambooweekly.com
In the latest Bamboo Weekly, we use Pandas to analyze data about Kalshi's markets.
Level up your data-analysis skills every Wednesday: bambooweekly.com
December 24, 2025 at 4:15 PM
How much of the Kalshi prediction market's contracts are about sports? And did court rulings last October help their business?
In the latest Bamboo Weekly, we use Pandas to analyze data about Kalshi's markets.
Level up your data-analysis skills every Wednesday: bambooweekly.com
In the latest Bamboo Weekly, we use Pandas to analyze data about Kalshi's markets.
Level up your data-analysis skills every Wednesday: bambooweekly.com
Does your data include dates and times?
In #Python #Pandas 3, datetimes are stored in microseconds (us) by default, not ns. My latest video explains what's going on: www.youtube.com/watch?v=poQo...
Catch this, and my entire "Prep for Pandas 3" playlist: youtu.be/poQo-V-3Gp4?...
In #Python #Pandas 3, datetimes are stored in microseconds (us) by default, not ns. My latest video explains what's going on: www.youtube.com/watch?v=poQo...
Catch this, and my entire "Prep for Pandas 3" playlist: youtu.be/poQo-V-3Gp4?...
Microseconds vs nanoseconds: datetime64 changes in Pandas 3
Pandas 3 is changing from a default of nanoseconds to microseconds. What does this mean for you?
In this video, I show what the implications are when parsing dates from strings, and when converting…
www.youtube.com
December 23, 2025 at 8:00 PM
Does your data include dates and times?
In #Python #Pandas 3, datetimes are stored in microseconds (us) by default, not ns. My latest video explains what's going on: www.youtube.com/watch?v=poQo...
Catch this, and my entire "Prep for Pandas 3" playlist: youtu.be/poQo-V-3Gp4?...
In #Python #Pandas 3, datetimes are stored in microseconds (us) by default, not ns. My latest video explains what's going on: www.youtube.com/watch?v=poQo...
Catch this, and my entire "Prep for Pandas 3" playlist: youtu.be/poQo-V-3Gp4?...
What did I do in 2025?
In a nutshell: Lots of teaching #Python and #Pandas, writing books and newsletters, recording videos, and traveling -- with lots more planned for 2026!
You can see my writeup here: lerner.co.il/2025/12/23/r...
In a nutshell: Lots of teaching #Python and #Pandas, writing books and newsletters, recording videos, and traveling -- with lots more planned for 2026!
You can see my writeup here: lerner.co.il/2025/12/23/r...
Reuven's 2025 in review
Can you believe that 2025 is almost over? It was full of big events for me, and yet it also whizzed past at breakneck speed. And so, before we start 2026, I want to share
lerner.co.il
December 23, 2025 at 6:17 PM
What did I do in 2025?
In a nutshell: Lots of teaching #Python and #Pandas, writing books and newsletters, recording videos, and traveling -- with lots more planned for 2026!
You can see my writeup here: lerner.co.il/2025/12/23/r...
In a nutshell: Lots of teaching #Python and #Pandas, writing books and newsletters, recording videos, and traveling -- with lots more planned for 2026!
You can see my writeup here: lerner.co.il/2025/12/23/r...
#Python #Pandas 3 is coming soon — and it's different from Pandas 2.
I just released two new videos:
• inplace=True now sometimes returns a value: youtu.be/VySIM5CW8Kw
• SettingWithCopyWarning has gone away, thanks to copy on write: youtu.be/wITIN2DOXtU
What questions do you have about Pandas 3?
I just released two new videos:
• inplace=True now sometimes returns a value: youtu.be/VySIM5CW8Kw
• SettingWithCopyWarning has gone away, thanks to copy on write: youtu.be/wITIN2DOXtU
What questions do you have about Pandas 3?
December 22, 2025 at 12:52 PM
#Python #Pandas 3 is coming soon — and it's different from Pandas 2.
I just released two new videos:
• inplace=True now sometimes returns a value: youtu.be/VySIM5CW8Kw
• SettingWithCopyWarning has gone away, thanks to copy on write: youtu.be/wITIN2DOXtU
What questions do you have about Pandas 3?
I just released two new videos:
• inplace=True now sometimes returns a value: youtu.be/VySIM5CW8Kw
• SettingWithCopyWarning has gone away, thanks to copy on write: youtu.be/wITIN2DOXtU
What questions do you have about Pandas 3?
#Python #Pandas 3 is coming out soon — and a lot of things are changing.
To help you prepare, I've got new videos on my YouTube channel.
Get them all at my new Pandas 3 playlist: www.youtube.com/playlist?lis...
To help you prepare, I've got new videos on my YouTube channel.
Get them all at my new Pandas 3 playlist: www.youtube.com/playlist?lis...
Pandas 3 — what you need to know - YouTube
Pandas 3.0 is coming out soon, and changes the way we work with our data. In this playlist, I'll explain what is going on, and help you to prepare for this t...
www.youtube.com
December 21, 2025 at 2:40 PM
#Python #Pandas 3 is coming out soon — and a lot of things are changing.
To help you prepare, I've got new videos on my YouTube channel.
Get them all at my new Pandas 3 playlist: www.youtube.com/playlist?lis...
To help you prepare, I've got new videos on my YouTube channel.
Get them all at my new Pandas 3 playlist: www.youtube.com/playlist?lis...
How many people who feel sick actually have the flu? In the latest Bamboo Weekly, we compared numbers from last year and this year for each HHS region.
Oh, and we compare memory, speed, and syntax of #Pandas 2 vs. 3.
Level up your Pandas with real-world questions and data sets: bambooweekly.com
Oh, and we compare memory, speed, and syntax of #Pandas 2 vs. 3.
Level up your Pandas with real-world questions and data sets: bambooweekly.com
December 18, 2025 at 8:05 PM
How many people who feel sick actually have the flu? In the latest Bamboo Weekly, we compared numbers from last year and this year for each HHS region.
Oh, and we compare memory, speed, and syntax of #Pandas 2 vs. 3.
Level up your Pandas with real-world questions and data sets: bambooweekly.com
Oh, and we compare memory, speed, and syntax of #Pandas 2 vs. 3.
Level up your Pandas with real-world questions and data sets: bambooweekly.com
In the latest Bamboo Weekly, we examine the recent spread of flu in the US with data from the CDC.
Better yet: We compare Pandas 2 and Pandas 3 for speed, memory, and style.
You'll feel better after solving these real-world data problems! Check them out at bambooweekly.com
Better yet: We compare Pandas 2 and Pandas 3 for speed, memory, and style.
You'll feel better after solving these real-world data problems! Check them out at bambooweekly.com
December 18, 2025 at 12:15 AM
In the latest Bamboo Weekly, we examine the recent spread of flu in the US with data from the CDC.
Better yet: We compare Pandas 2 and Pandas 3 for speed, memory, and style.
You'll feel better after solving these real-world data problems! Check them out at bambooweekly.com
Better yet: We compare Pandas 2 and Pandas 3 for speed, memory, and style.
You'll feel better after solving these real-world data problems! Check them out at bambooweekly.com
This month marks 30 years (!) since I left the corporate world and started freelancing. To celebrate, here are 30 lessons I've learned about being a #Python freelancer:
lerner.co.il/2025/12/08/3...
lerner.co.il/2025/12/08/3...
30 things I’ve learned from 30 years as a Python freelancer
30 years! It’s hard to believe, but it was in December 1995 (i.e., 30 years ago) that I went freelance, giving up a stable corporate paycheck. And somehow, I’ve managed to make it work: During
lerner.co.il
December 8, 2025 at 12:30 PM
This month marks 30 years (!) since I left the corporate world and started freelancing. To celebrate, here are 30 lessons I've learned about being a #Python freelancer:
lerner.co.il/2025/12/08/3...
lerner.co.il/2025/12/08/3...
Presidential pardons are in the news. In the latest Bamboo Weekly, we analyze pardon data from the Department of Justice.
Level up your #Python and #Pandas skills, including Web scraping, cleaning, grouping, and plotting!
New questions every week at bambooweekly.com .
Level up your #Python and #Pandas skills, including Web scraping, cleaning, grouping, and plotting!
New questions every week at bambooweekly.com .
December 4, 2025 at 10:51 PM
Presidential pardons are in the news. In the latest Bamboo Weekly, we analyze pardon data from the Department of Justice.
Level up your #Python and #Pandas skills, including Web scraping, cleaning, grouping, and plotting!
New questions every week at bambooweekly.com .
Level up your #Python and #Pandas skills, including Web scraping, cleaning, grouping, and plotting!
New questions every week at bambooweekly.com .
Do you use #Jupyter with #Python #Pandas?
You should check out @marimo.io, a notebook that solves many Jupyter's issues.
My talk from last month's @PyDataTLV introduced and demo'ed Marimo, with live demos of its features.
Take a look: youtu.be/koAgUxKndNU
You should check out @marimo.io, a notebook that solves many Jupyter's issues.
My talk from last month's @PyDataTLV introduced and demo'ed Marimo, with live demos of its features.
Take a look: youtu.be/koAgUxKndNU
Reuven Lerner: Marimo - A new notebook | PyData Tel Aviv 2025
YouTube video by PyData
youtu.be
December 4, 2025 at 5:47 PM
Do you use #Jupyter with #Python #Pandas?
You should check out @marimo.io, a notebook that solves many Jupyter's issues.
My talk from last month's @PyDataTLV introduced and demo'ed Marimo, with live demos of its features.
Take a look: youtu.be/koAgUxKndNU
You should check out @marimo.io, a notebook that solves many Jupyter's issues.
My talk from last month's @PyDataTLV introduced and demo'ed Marimo, with live demos of its features.
Take a look: youtu.be/koAgUxKndNU
Last month, I published a free, 12-part "uv crash course". Hundreds of people took it, and are now using #Python uv better.
But: I keep learning new things. So I've updated the course to have *15* lessons.
Feel like you aren't using uv correctly? Check out the free course at uvcrashcourse.com !
But: I keep learning new things. So I've updated the course to have *15* lessons.
Feel like you aren't using uv correctly? Check out the free course at uvcrashcourse.com !
uv crash course - LernerPython
uvCrashCourse.com
December 3, 2025 at 12:21 AM
Last month, I published a free, 12-part "uv crash course". Hundreds of people took it, and are now using #Python uv better.
But: I keep learning new things. So I've updated the course to have *15* lessons.
Feel like you aren't using uv correctly? Check out the free course at uvcrashcourse.com !
But: I keep learning new things. So I've updated the course to have *15* lessons.
Feel like you aren't using uv correctly? Check out the free course at uvcrashcourse.com !
Traveling for Thanksgiving? So are lots of other people!
But is this really the busiest travel period of the year?
In the latest Bamboo Weekly, we look at US travel trends using TSA data.
Improve your #Python #Pandas data-analysis skills every week: bambooweekly.com
But is this really the busiest travel period of the year?
In the latest Bamboo Weekly, we look at US travel trends using TSA data.
Improve your #Python #Pandas data-analysis skills every week: bambooweekly.com
November 26, 2025 at 7:30 PM
Traveling for Thanksgiving? So are lots of other people!
But is this really the busiest travel period of the year?
In the latest Bamboo Weekly, we look at US travel trends using TSA data.
Improve your #Python #Pandas data-analysis skills every week: bambooweekly.com
But is this really the busiest travel period of the year?
In the latest Bamboo Weekly, we look at US travel trends using TSA data.
Improve your #Python #Pandas data-analysis skills every week: bambooweekly.com
Reposted by Reuven M. Lerner
Are you a #Python user and a lifelong learner?
I've just published my 8th annual list of every Python-related Black Friday / Cyber Monday sale I'm aware of.
I've just published my 8th annual list of every Python-related Black Friday / Cyber Monday sale I'm aware of.
Python Black Friday & Cyber Monday sales (2025)
It’s time for some discounted Python-related skill-building.
This is my eighth annual compilation of Python learning-related Black Friday & …
treyhunner.com
November 24, 2025 at 4:41 PM
Are you a #Python user and a lifelong learner?
I've just published my 8th annual list of every Python-related Black Friday / Cyber Monday sale I'm aware of.
I've just published my 8th annual list of every Python-related Black Friday / Cyber Monday sale I'm aware of.
How is the US economy doing?
In the latest Bamboo Weekly, I challenge you to find out:
• Retrieve 8 indicators from FRED
• Combine them in a Pandas data frame
• Filter them with Marimo UI elements
• Plot them with Plotly
Get new real-world exercises each week: bambooweekly.com
In the latest Bamboo Weekly, I challenge you to find out:
• Retrieve 8 indicators from FRED
• Combine them in a Pandas data frame
• Filter them with Marimo UI elements
• Plot them with Plotly
Get new real-world exercises each week: bambooweekly.com
November 19, 2025 at 6:00 PM
How is the US economy doing?
In the latest Bamboo Weekly, I challenge you to find out:
• Retrieve 8 indicators from FRED
• Combine them in a Pandas data frame
• Filter them with Marimo UI elements
• Plot them with Plotly
Get new real-world exercises each week: bambooweekly.com
In the latest Bamboo Weekly, I challenge you to find out:
• Retrieve 8 indicators from FRED
• Combine them in a Pandas data frame
• Filter them with Marimo UI elements
• Plot them with Plotly
Get new real-world exercises each week: bambooweekly.com
• Frustrated that after learning #Python, you still don't 'understand how it works?
• Want at structured learning path to improve your Python?
• Want to feel more comfortable at interviews?
• Tired of data exercises that are tiny or fake?
• Want at structured learning path to improve your Python?
• Want to feel more comfortable at interviews?
• Tired of data exercises that are tiny or fake?
November 16, 2025 at 4:00 PM
• Frustrated that after learning #Python, you still don't 'understand how it works?
• Want at structured learning path to improve your Python?
• Want to feel more comfortable at interviews?
• Tired of data exercises that are tiny or fake?
• Want at structured learning path to improve your Python?
• Want to feel more comfortable at interviews?
• Tired of data exercises that are tiny or fake?
In today's Bamboo Weekly, I pose 5 data-analysis questions about museum heists — based on a recent paper, and the recent theft from the Louvre in Paris.
Use grouping, regular expressions, and multi-indexes to analyze heist data!
Improve your Pandas skills every Wednesday: bambooweekly.com
Use grouping, regular expressions, and multi-indexes to analyze heist data!
Improve your Pandas skills every Wednesday: bambooweekly.com
November 12, 2025 at 5:00 PM
In today's Bamboo Weekly, I pose 5 data-analysis questions about museum heists — based on a recent paper, and the recent theft from the Louvre in Paris.
Use grouping, regular expressions, and multi-indexes to analyze heist data!
Improve your Pandas skills every Wednesday: bambooweekly.com
Use grouping, regular expressions, and multi-indexes to analyze heist data!
Improve your Pandas skills every Wednesday: bambooweekly.com
Do you use Python, but...
• want to go beyond the syntax?
• want to feel confident in interviews?
• want to work on real data projects?
A new cohort of my #Python Data Analytics Bootcamp is starting soon! Join me on November 18th for a free info session.
More info: pythondab.com
• want to go beyond the syntax?
• want to feel confident in interviews?
• want to work on real data projects?
A new cohort of my #Python Data Analytics Bootcamp is starting soon! Join me on November 18th for a free info session.
More info: pythondab.com
PythonDAB — Reuven's Python Analytics Bootcamp - LernerPython
Start your new career in Data Analytics
PythonDAB.com
November 11, 2025 at 8:00 PM
Do you use Python, but...
• want to go beyond the syntax?
• want to feel confident in interviews?
• want to work on real data projects?
A new cohort of my #Python Data Analytics Bootcamp is starting soon! Join me on November 18th for a free info session.
More info: pythondab.com
• want to go beyond the syntax?
• want to feel confident in interviews?
• want to work on real data projects?
A new cohort of my #Python Data Analytics Bootcamp is starting soon! Join me on November 18th for a free info session.
More info: pythondab.com
uv makes #Python packaging it fast, easy, and modern — replacing everything from pip, pyenv, and pipx to twine, venv, and Poetry.
If you’ve been wondering whether — and how — to switch to uv and use it, my free, 12-part course will you everything you need.
Take a look: youtu.be/PrRQC3_6scQ
If you’ve been wondering whether — and how — to switch to uv and use it, my free, 12-part course will you everything you need.
Take a look: youtu.be/PrRQC3_6scQ
Learn uv with my all-new "uv crash course", at https://uvcrashcourse.com
YouTube video by Python and Pandas with Reuven Lerner
youtu.be
November 10, 2025 at 1:07 PM
uv makes #Python packaging it fast, easy, and modern — replacing everything from pip, pyenv, and pipx to twine, venv, and Poetry.
If you’ve been wondering whether — and how — to switch to uv and use it, my free, 12-part course will you everything you need.
Take a look: youtu.be/PrRQC3_6scQ
If you’ve been wondering whether — and how — to switch to uv and use it, my free, 12-part course will you everything you need.
Take a look: youtu.be/PrRQC3_6scQ
In the latest Bamboo Weekly, I pose data-analysis questions about cellphones in schools:
• What policies do schools have?
° Do rules differ by age or region?
• What effects (positive and negative) do schools report from phone use?
Level up your #Python #Pandas skills every week: bambooweekly.com
• What policies do schools have?
° Do rules differ by age or region?
• What effects (positive and negative) do schools report from phone use?
Level up your #Python #Pandas skills every week: bambooweekly.com
November 7, 2025 at 11:00 AM
In the latest Bamboo Weekly, I pose data-analysis questions about cellphones in schools:
• What policies do schools have?
° Do rules differ by age or region?
• What effects (positive and negative) do schools report from phone use?
Level up your #Python #Pandas skills every week: bambooweekly.com
• What policies do schools have?
° Do rules differ by age or region?
• What effects (positive and negative) do schools report from phone use?
Level up your #Python #Pandas skills every week: bambooweekly.com
Assignment in #Python seems so simple... but when you use =, a lot of different things can happen!
In my talk from @europython.eu, I described what happens when you use =, from variables to attributes to descriptors -- including the behind-the-scenes opcodes.
Take a look: youtu.be/0eSutJEeR5c
In my talk from @europython.eu, I described what happens when you use =, from variables to attributes to descriptors -- including the behind-the-scenes opcodes.
Take a look: youtu.be/0eSutJEeR5c
What does = do? — Reuven M. Lerner
YouTube video by EuroPython Conference
youtu.be
November 4, 2025 at 7:25 AM
Assignment in #Python seems so simple... but when you use =, a lot of different things can happen!
In my talk from @europython.eu, I described what happens when you use =, from variables to attributes to descriptors -- including the behind-the-scenes opcodes.
Take a look: youtu.be/0eSutJEeR5c
In my talk from @europython.eu, I described what happens when you use =, from variables to attributes to descriptors -- including the behind-the-scenes opcodes.
Take a look: youtu.be/0eSutJEeR5c
Want to learn uv?
uv has taken the #Python world by storm. But using it isn't just about learning a few commands.
That's where my new, free, 12-part "uv crash course" comes in. Every day, you'll get detailed e-mail with info about using uv.
Sign up: uvcrashcourse.com
uv has taken the #Python world by storm. But using it isn't just about learning a few commands.
That's where my new, free, 12-part "uv crash course" comes in. Every day, you'll get detailed e-mail with info about using uv.
Sign up: uvcrashcourse.com
November 3, 2025 at 1:11 PM
Want to learn uv?
uv has taken the #Python world by storm. But using it isn't just about learning a few commands.
That's where my new, free, 12-part "uv crash course" comes in. Every day, you'll get detailed e-mail with info about using uv.
Sign up: uvcrashcourse.com
uv has taken the #Python world by storm. But using it isn't just about learning a few commands.
That's where my new, free, 12-part "uv crash course" comes in. Every day, you'll get detailed e-mail with info about using uv.
Sign up: uvcrashcourse.com
How do you connect #FastAPI to a database?
In this 30-minute tutorial, I create a simple FastAPI app that implements a blog — starting with uv, then going onto an SQLModel class, then going through the various FastAPI functions we need for it to work.
Have a look: www.youtube.com/watch?v=eZGy...
In this 30-minute tutorial, I create a simple FastAPI app that implements a blog — starting with uv, then going onto an SQLModel class, then going through the various FastAPI functions we need for it to work.
Have a look: www.youtube.com/watch?v=eZGy...
Getting started with FastAPI and SQLModel — Build a simple blog API (full tutorial)
YouTube video by Python and Pandas with Reuven Lerner
www.youtube.com
October 31, 2025 at 8:54 AM
How do you connect #FastAPI to a database?
In this 30-minute tutorial, I create a simple FastAPI app that implements a blog — starting with uv, then going onto an SQLModel class, then going through the various FastAPI functions we need for it to work.
Have a look: www.youtube.com/watch?v=eZGy...
In this 30-minute tutorial, I create a simple FastAPI app that implements a blog — starting with uv, then going onto an SQLModel class, then going through the various FastAPI functions we need for it to work.
Have a look: www.youtube.com/watch?v=eZGy...
Hurricane Melissa is causing awful damage. In the latest Bamboo Weekly, I pose six problems based on NOAA hurricane data -- using grouping, resampling, and plotting on windspeed and even their names.
Check out bambooweekly.com, and level up your Pandas skills!
Check out bambooweekly.com, and level up your Pandas skills!
October 30, 2025 at 7:00 PM
Hurricane Melissa is causing awful damage. In the latest Bamboo Weekly, I pose six problems based on NOAA hurricane data -- using grouping, resampling, and plotting on windspeed and even their names.
Check out bambooweekly.com, and level up your Pandas skills!
Check out bambooweekly.com, and level up your Pandas skills!