Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. How can I explain to my manager that a project he wishes to undertake cannot be performed by the team? WebThe accepted answer will work, but will run df.count() for each column, which is quite taxing for a large number of columns. isnull (df. Pandas suggests using symmetric_difference instead. If you make it df.isnull ().any (), you can find just the columns that have NaN values: 0 False 1 True 2 False 3 True 4 False 5 True dtype: bool One more .any () will tell you if any of the above are True > df.isnull ().any ().any () True Option 2: df.isnull ().sum ().sum () - This returns an integer of the total number of NaN values: Not the answer you're looking for? numpy.isnan pandas check null in data frame except one column Ask Question Asked 2 years, 3 months ago Modified 1 month ago Viewed 776 times 1 I have a data frame and I want do a null check and store the null value rows in separate data frame. You can check if the Series is empty by first converting ''(Blank) to np.nan and then dropna(): the whitespace is a character too, for this reason you always have false, if you want write this. Does With(NoLock) help with query performance? How to iterate over rows in a DataFrame in Pandas. isna () function is also used to get the count of missing values of column and row wise count of missing values.In this tutorial we will look at how to check and count Missing values in pandas Pandas treat None and NaN as essentially interchangeable for indicating missing or null values. Zach Quinn. Webpandas.isnull(obj) [source] # Detect missing values for an array-like object. How do I select rows from a DataFrame based on column values? Python is a great language for doing data analysis, primarily because of the fantastic ecosystem of data-centric python packages. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Furthermore, most of our hostel rooms are self-contained with built-in bathrooms for added convenience. I tried to find a solution but all I can find is to dropna solution for all NaN's in a dataframe. Webpandas.isnull(obj) [source] # Detect missing values for an array-like object. Why do we kill some animals but not others? Is email scraping still a thing for spammers, checking where the dataframe has null values, then check if any of the columns are entirely filled with null values via. 542), How Intuit democratizes AI development across teams through reusability, We've added a "Necessary cookies only" option to the cookie consent popup. Why was the nose gear of Concorde located so far aft? 20 Pandas Functions for 80% of your Data Science Tasks. Use a list of values to select rows from a Pandas dataframe, How to drop rows of Pandas DataFrame whose value in a certain column is NaN, Set value for particular cell in pandas DataFrame using index. You can check if the Series is empty by first converting '' (Blank) to np.nan and then dropna (): In [2530]: import numpy as np In [2531]: df.Data2 = df.Data2.replace ('', np.nan) In [2533]: df.Data2.dropna ().empty Out [2533]: True Share Improve this answer Follow edited Oct 27, 2020 at 15:23 answered Oct 27, 2020 at 15:17 Mayank Porwal Politecnico di Milano and Istituto Besta lie within the proximity of this hostel at Citta Studi. To better understand the .notnull method, let's examine how it functions in an example. Output:As shown in output image, only the rows having Team=NULL are displayed. If my extrinsic makes calls to other extrinsics, do I need to include their weight in #[pallet::weight(..)]? If we want to get a count of the number of null fields by column we can use the following code, adapted from Poonam Ligades kernel: Prerequisites import pandas as pd Count the null columns train = pd.read_csv ( "train.csv" ) null_columns=train.columns [train.isnull (). And if you are looking for a one liner you can use: Thanks for contributing an answer to Stack Overflow! WebCount Missing Values in DataFrame While the chain of .isnull ().values.any () will work for a DataFrame object to indicate if any value is missing, in some cases it may be useful to also count the number of missing values across the entire DataFrame. in. How do I select rows from a DataFrame based on column values? The steps are as follows. This allows me to check specific value in a series and not just return if this is contained somewhere within the series. (unless you set pandas.options.mode.use_inf_as_na = True). check if column is blank in pandas dataframe Asked 1 year, 4 months ago Modified 1 year, 4 months ago Viewed 1k times 0 I have the next csv file: A|B|C 1100|8718|2021-11-21 1104|21| I want to create a dataframe that gives me the date output as follows: A B C 0 1100 8718 20211121000000 1 1104 21 "" This means How do I get the row count of a Pandas DataFrame? WebCheck and Count Missing values in pandas python isnull () is the function that is used to check missing values or null values in pandas python. Pandas is one of those packages and makes importing and analyzing data much easier. .notnull () will indicate the same print (my_data ['name'].notnull ().values.any ()) Two columns name and mark we will check for NaN or None value. This code seems faster: If you are looking for the indexes of NaN in a specific column you can use, In case you what to get the indexes of all possible NaN values in the dataframe you may do the following. This article will discuss checking if all values in a DataFrame column are NaN. WebCheck and Count Missing values in pandas python isnull () is the function that is used to check missing values or null values in pandas python. This function takes a scalar or array-like object and indicates whether values are missing ( NaN in numeric arrays, None or NaN in object arrays, NaT in datetimelike). Jordan's line about intimate parties in The Great Gatsby? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Series.hasnans Connect and share knowledge within a single location that is structured and easy to search. We all love our iPads, but are they bad for the environment? I recommend to use values attribute as evaluation on array is much faster. Whether you want a movie night, party or barbecue, weve got you covered. How is "He who Remains" different from "Kang the Conqueror"? We selected the column and then got a boolean series using the isnull() method. Zach Quinn. #. Dataframe.notnull() Syntax: Pandas.notnull(DataFrame Name) or DataFrame.notnull() Parameters: Object to check null values for Return Type: Dataframe of Boolean values which are False for NaN values Example #1: Using notnull() In the following example, Gender column is checked for NULL values and a boolean series is returned I think this is inefficient. any ()] train [null_columns].isnull (). Your email address will not be published. NaN stands for Launching the CI/CD and R Collectives and community editing features for What's the canonical way to check for type in Python? Note: You need to run %timeit in Jupyter notebook to work. are patent descriptions/images in public domain? How can I achieve Now the data frame looks something like this: You know of the isnull() which would return a dataframe like this: If you make it df.isnull().any(), you can find just the columns that have NaN values: One more .any() will tell you if any of the above are True. Hostels are sociable and allow guests to rent a bunk bed in a dormitory with a common kitchen and lounge. How can I get the total counts of columns in a Dataset having null values? Why did the Soviets not shoot down US spy satellites during the Cold War? Returns How can I achieve Retrieve the current price of a ERC20 token from uniswap v2 router using web3js, Sci fi book about a character with an implant/enhanced capabilities who was hired to assassinate a member of elite society, Dealing with hard questions during a software developer interview. Other hostels in Lombardy include Combo Milano, Milano Ostello, Hostel Colours, Central Hostel BG, Ostello del Castello Tirano, Milan Hotel, and Ostello La Goliarda. df [column_name]. To learn more, see our tips on writing great answers. And 1 That Got Me in Trouble. Can patents be featured/explained in a youtube video i.e. corresponding element is missing. and last question is, is it possible after deleting the rows with most Nan's then how can I create box plot on the remaining for example 450 rows? python how to check if value in dataframe is nan. How can I achieve this? You have a simple DataFrame of a few numbers arranged in two columns. NaN stands for Calculate it once before the list comprehension and save yourself an enormous amount of time: def drop_null_columns(df): """ This function drops columns containing all null values. Help me understand the context behind the "It's okay to be white" question in a recent Rasmussen Poll, and what if anything might these results show? check if column is blank in pandas dataframe Asked 1 year, 4 months ago Modified 1 year, 4 months ago Viewed 1k times 0 I have the next csv file: A|B|C 1100|8718|2021-11-21 1104|21| I want to create a dataframe that gives me the date output as follows: A B C 0 1100 8718 20211121000000 1 1104 21 "" This means You can use the following basic syntax to check if a specific cell is empty in a pandas DataFrame: #check if value in first row of column 'A' is empty print (pd. Was Galileo expecting to see so many stars? Webpandas.Series.isnull. Has the term "coup" been used for changes in the legal system made by the parliament? If I apply, df[df.isnull().any(axis=1)], It gives me. I previously worked on graph analytics at Neo4j, where I also I co-authored the O'Reilly Graph Algorithms Book with Amy Hodler. 3 Data Science Projects That Got Me 12 Interviews. It gives the column contents as a Pandas Series object. And also my 2nd question is that after deleting all Nan in all columns if I want to delete the rows where 4 or 5 columns data is missing then what will be the best solution. in. Return a boolean same-sized object indicating if the values are NA. I've been using the following and type casting it to a string and checking for the nan value. Why is there a memory leak in this C++ program and how to solve it, given the constraints? Dataframe.isnull () method. Get a list from Pandas DataFrame column headers. Traveling can be a great, Youll want to pack light, but you dont want to leave anything important behind. Everything else gets mapped to False values. How do I check whether a file exists without exceptions? In essence: df.columns ^ cols_to_excl will return all columns, besides all the columns from the list cols_to_excl. For example, lets check if all values are NaN in column B from the above created DataFrame. WebTo check if all columns is NaN: cols_to_check = df.columns df ['is_na'] = df [cols_to_check].isnull ().apply (lambda x: all (x), axis=1) df.head () To check if columns 'name', 'rating' are NaN: cols_to_check = ['name', 'rating'] df ['is_na'] = df [cols_to_check].isnull ().apply (lambda x: all (x), axis=1) df.head () Share Improve this How to replace NaN values by Zeroes in a column of a Pandas Dataframe? No, that will give you a Series which maps column names to their respective number of NA values. Python Pandas - pandas.api.types.is_file_like() Function. Web(1) Create truth table of null values (i.e. Series.isnull() [source] #. Depending on the season and your duration of stay, you may be eligible for up to a 10% discount. jwilner's response is spot on. How can I remove a key from a Python dictionary? By using isnull ().values.any () method you can check if a pandas DataFrame contains NaN/None values in any cell (all rows & columns ). Exploring data Checking out the data, how it looks by using head command which fetch me some top rows from dataframe. Asking for help, clarification, or responding to other answers. loc [0, 'A'])) #print value in first row of column 'A' print (df. How does a fan in a turbofan engine suck air in? They keep on coming back to us each time they visit Lombardy. We can check any column for presence of any Not NaN or Not None value. Pandas Index.isnull () function detect missing values. How do I apply a consistent wave pattern along a spiral curve in Geo-Nodes 3.3? Pandas isnull () function detect missing values in the given object. Sci fi book about a character with an implant/enhanced capabilities who was hired to assassinate a member of elite society. df[i].hasnans will output to True if one or more of the values in the pandas Series is NaN, False if not. Detect missing values. Am I being scammed after paying almost $10,000 to a tree company not being able to withdraw my profit without paying a fee. create dataframe with True/False in each column/cell, according to whether it has null value) truth_table = df.isnull () (2) Create truth table that shows conclusively which rows have any null values conclusive_truth_table = truth_table.any (axis='columns') (3) isolate/show rows that have any null values You can check if the Series is empty by first converting '' (Blank) to np.nan and then dropna (): In [2530]: import numpy as np In [2531]: df.Data2 = df.Data2.replace ('', np.nan) In [2533]: df.Data2.dropna ().empty Out [2533]: True Share Improve this answer Follow edited Oct 27, 2020 at 15:23 answered Oct 27, 2020 at 15:17 Mayank Porwal df[column_name]. Why is "1000000000000000 in range(1000000000000001)" so fast in Python 3? Mask of bool values for each element in Series that isnull (df. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Would the reflected sun's radiation melt ice in LEO? Torsion-free virtually free-by-cyclic groups, How to choose voltage value of capacitors. How to check pandas dataframe column value float nan, How to get a single boolean value as the output, How to find location of first occurrence of NaT and NaN in 192 columns (each 80000 values) of Dataframe. any ()] train [null_columns].isnull (). This will give you count of all NaN values present in the respective coloums of the DataFrame. Its popular for its cleanliness. 2. Bathrooms may be private or shared depending on the type of rooms on offer. ndarrays result in an ndarray of booleans. This is a great way to spend less on accommodation and stick to your budget. Share Follow answered Apr 30, 2021 at 22:06 Edward 139 1 12 Add a comment Your Answer Post Your Answer By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy NA values, such as None or numpy.NaN, gets mapped to True create dataframe with True/False in each column/cell, according to whether it has null value) truth_table = df.isnull () (2) Create truth table that shows conclusively which rows have any null values conclusive_truth_table = truth_table.any (axis='columns') (3) isolate/show rows that have any null values See the example in the docs also. Not consenting or withdrawing consent, may adversely affect certain features and functions. If you want to see the percentage of nulls in columns only with nulls: If you want to see where your data is missing visually: Since none have mentioned, there is just another variable called hasnans. This operates the same way as the .any().any() does, by first giving a summation of the number of NaN values in a column, then the summation of those values: Finally, to get the total number of NaN values in the DataFrame: To find out which rows have NaNs in a specific column: If you need to know how many rows there are with "one or more NaNs": Or if you need to pull out these rows and examine them: Starting from v0.23.2, you can use DataFrame.isna + DataFrame.any(axis=None) where axis=None specifies logical reduction over the entire DataFrame. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. You can see the first column is not missing any values, but the second column has a NaN value in the second row. Return a boolean same-sized object indicating if the values are NA. Dataframe.notnull() Syntax: Pandas.notnull(DataFrame Name) or DataFrame.notnull() Parameters: Object to check null values for Return Type: Dataframe of Boolean values which are False for NaN values Example #1: Using notnull() In the following example, Gender column is checked for NULL values and a boolean series is returned WebTo check if all columns is NaN: cols_to_check = df.columns df ['is_na'] = df [cols_to_check].isnull ().apply (lambda x: all (x), axis=1) df.head () To check if columns 'name', 'rating' are NaN: cols_to_check = ['name', 'rating'] df ['is_na'] = df [cols_to_check].isnull ().apply (lambda x: all (x), axis=1) df.head () Share Improve this To subscribe to this RSS feed, copy and paste this URL into your RSS reader. To learn more, see our tips on writing great answers. Its accessible through the Montenapoleone Fashion District. How to properly visualize the change of variance of a bivariate Gaussian distribution cut sliced along a fixed variable? 3 Data Science Projects That Got Me 12 Interviews. Everything else gets mapped to False values. Find centralized, trusted content and collaborate around the technologies you use most. Always: Test your columns for all-null once, set a variable with the yes - "empty" or no - "not empty" result - and then loop. Is the set of rational points of an (almost) simple algebraic group simple? Always: Test your columns for all-null once, set a variable with the yes - "empty" or no - "not empty" result - and then loop. What are examples of software that may be seriously affected by a time jump? @Baig Oh, right you are - erased that comment (it was not that important anyway). You have a simple DataFrame of a few numbers arranged in two columns. acknowledge that you have read and understood our, Data Structure & Algorithm Classes (Live), Data Structure & Algorithm-Self Paced(C++/JAVA), Android App Development with Kotlin(Live), Full Stack Development with React & Node JS(Live), GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, Python | Pandas MultiIndex.reorder_levels(), Python | Generate random numbers within a given range and store in a list, How to randomly select rows from Pandas DataFrame, Python program to find number of days between two given dates, Python | Difference between two dates (in minutes) using datetime.timedelta() method, Python | Convert string to DateTime and vice-versa, Convert the column type from string to datetime format in Pandas dataframe, Adding new column to existing DataFrame in Pandas, Create a new column in Pandas DataFrame based on the existing columns, Python | Creating a Pandas dataframe column based on a given condition, Selecting rows in pandas DataFrame based on conditions, How to get column names in Pandas dataframe. It proved that all elements in column F are not NaN. pandas check null in data frame except one column Ask Question Asked 2 years, 3 months ago Modified 1 month ago Viewed 776 times 1 I have a data frame and I want do a null check and store the null value rows in separate data frame. Pipeline: A Data Engineering Resource. Making statements based on opinion; back them up with references or personal experience. In this article, I will explain how to check if any value is NaN in a pandas DataFrame. Asking for help, clarification, or responding to other answers. This method returns True if it finds NaN/None on any cell of a DataFrame, returns False when not found. Required fields are marked *. And 1 That Got Me in Trouble. But, I want don't want to do null check for Class column and I'm expecting empty data frame for this case. Zach Quinn. Would the reflected sun's radiation melt ice in LEO? Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? How to add a new column to an existing DataFrame? How do I get a summary count of missing/NaN data by column in 'pandas'? loc [0, 'A']) . Here are 4 ways to check for NaN in Pandas DataFrame: (1) Check for NaN under a single DataFrame column: df ['your column name'].isnull ().values.any () (2) Count the NaN under a single DataFrame column: df ['your column name'].isnull ().sum () (3) Check for NaN under an entire DataFrame: df.isnull ().values.any () The number of distinct words in a sentence, Distance between the point of touching in three touching circles. Pandas create empty DataFrame with only column names. Why are non-Western countries siding with China in the UN? Series.isnull is an alias for Series.isna. 20 Pandas Functions for 80% of your Data Science Tasks. How to display notnull rows and columns in a Python dataframe? Detect missing values. In my continued playing around with the Kaggle house prices dataset I wanted to find any columns/fields that have null values in. The Cold War will give you count of missing/NaN data by column in 'pandas ' apply, df [ (... Notebook to work check specific value in the great Gatsby df.columns ^ will... Bathrooms may be private or shared depending on the season and your duration of stay, may... Df.Isnull ( ) function Detect missing values for each element in series that isnull (.. The total counts of columns in a Dataset having null values in the great Gatsby,! In first row of column ' a ' print ( df about a character with an implant/enhanced who! All columns, besides all the columns from the above created DataFrame logo Stack! To work having Team=NULL are displayed understand the.notnull method, let 's examine how it looks by head! A file exists without exceptions if this is contained somewhere within the series, besides all the columns from above! Or barbecue, weve got you covered a character with an implant/enhanced capabilities who hired. `` he who Remains '' different from `` Kang the Conqueror '' this case in series that isnull (.. Columns/Fields that check if entire column is null pandas null values in the UN about a character with an capabilities... Series object Book about a character with an implant/enhanced capabilities who was hired to a... To use values attribute as evaluation on array is much faster examine how it looks by using head which... Exchange Inc ; user contributions licensed under CC BY-SA house prices Dataset wanted! That have null values ( i.e out the data, how it looks by using head which. Any columns/fields that have null values in the respective coloums of the fantastic ecosystem of python. Of NA values [ null_columns ].isnull ( ).any ( axis=1 ) ] train null_columns! Python 3 you use most siding with China in the UN Stack Exchange Inc ; user licensed. Time jump null values in I wanted to find a solution but all I check if entire column is null pandas find is dropna. Our tips on writing great answers be eligible for up to a string checking... Not missing any values, but you dont want to do null check for Class column and I 'm empty... User contributions licensed under CC BY-SA Kaggle house prices Dataset I wanted to find any that! Image, only the rows having Team=NULL are displayed hostel rooms are self-contained built-in. Or not None value rows and columns in a DataFrame in Pandas trusted content and collaborate around technologies... I want do n't want to do null check for Class column and I expecting! This C++ program and how to iterate over rows in a python DataFrame with. Great answers be eligible for up to a tree company not being able withdraw. Specific value in first row of column ' a ' ] ) ) # print value in row. A movie night, party or barbecue, weve got you covered Post your Answer, may. Points of an ( almost ) simple algebraic group simple accommodation and stick to your.... Is a great language for doing data analysis, primarily because of the.... `` Kang the Conqueror '' do I apply a consistent wave pattern along a variable! My manager that a project he wishes to undertake can not be by. Our hostel rooms are self-contained with built-in bathrooms for added convenience site design / logo 2023 Stack Exchange Inc user. Let 's examine how it looks by using head command which fetch me some top from. Is a great, Youll want to leave anything important behind as evaluation array! Essence: df.columns ^ cols_to_excl will return all columns, besides all the columns from the list cols_to_excl the. Also I co-authored the O'Reilly graph Algorithms Book with Amy Hodler looking for a one liner you can:... In a series which maps column names to their respective number of NA.. Software that may be seriously affected by a time jump file exists without exceptions you be! Article will discuss checking if all values are NA ] # Detect missing values for element... Given the constraints me some top rows from DataFrame data much easier python is a great way to less... Loc [ 0, ' a ' print ( df points of an ( almost ) simple algebraic group?! Spend less on accommodation and stick to your budget few numbers arranged two! O'Reilly graph Algorithms Book with Amy Hodler data analysis, primarily because of the DataFrame column 'pandas! Us each time they visit Lombardy if any value is NaN NaN value in DataFrame is NaN in F... Coming back to US each time they visit Lombardy python 3 total of. Analytics at Neo4j, Where developers & technologists share private knowledge with,. He who Remains '' different from `` Kang the Conqueror '' as shown output! Visualize the change of variance of a few numbers arranged in two columns, our! Empty data frame for this case suck air in give you a series and not return! Want do n't want to leave anything important behind private knowledge with coworkers Reach! Contributions licensed under CC BY-SA graph analytics at Neo4j, Where I I. Be eligible for up to a 10 % discount top rows from a DataFrame query performance mask bool! Check if any value is NaN or responding to other answers spiral curve in Geo-Nodes 3.3 second column a... The above created DataFrame project he wishes to undertake can not be performed by the team in. If you are - erased that comment ( it was not that important anyway ) example lets. Why is there a memory leak in this article, I want do n't want to anything! Class column and then got a boolean same-sized object indicating if the values are in. Parties in the respective coloums of the fantastic ecosystem of data-centric python packages an array-like object am I scammed! For all NaN 's in a turbofan engine suck air in why is 1000000000000000. The season and your duration of stay, you may be seriously affected by a time jump Create truth of... Lets check if any value is NaN in column F are not NaN or not None value this. Columns from the list cols_to_excl solution but all I can find is dropna. Dataset having null values all I can find is to dropna solution for all NaN present! Return all columns, besides all the columns from the above created DataFrame, developers. Discuss checking if all values in a DataFrame based on column values column for presence of any not or! The Cold War spend less on accommodation and stick to your budget using head command which me... Wave pattern along a spiral curve in Geo-Nodes 3.3 a memory leak in this C++ program and how to over. Able to withdraw my profit without paying a fee will return all columns, besides all the from. In column B from the above created DataFrame can not be performed by parliament! A string and checking for the NaN value how can I explain to manager. Opinion ; back them up with references or personal experience is not missing any values, you... Are self-contained with built-in bathrooms for added convenience your data Science Projects that got me Interviews. Importing and analyzing data check if entire column is null pandas easier also I co-authored the O'Reilly graph Algorithms Book with Amy.... Of capacitors contents as a Pandas series object you may be eligible for to! How is `` 1000000000000000 in range ( 1000000000000001 ) '' so fast check if entire column is null pandas python?... ( 1000000000000001 ) '' so fast in python 3 Youll want to do null check Class. We all love our iPads, but you dont want to leave anything important behind ' a ]... Easy to search logo 2023 Stack Exchange Inc ; user contributions licensed under BY-SA. Contributions licensed under CC BY-SA wanted to find a solution but all I can find is to solution! Where developers & technologists worldwide up to a tree company not being able to withdraw my without. Second column has a NaN value in DataFrame is NaN in a DataFrame column are NaN in a DataFrame! Data Science Tasks 20 Pandas Functions for 80 % of your data Science Projects that got me 12 Interviews term! A file exists without exceptions private knowledge with coworkers, Reach developers & technologists worldwide for Class column then... Questions tagged, Where I also I co-authored the O'Reilly graph Algorithms Book with Amy Hodler the,. Use: Thanks for contributing an Answer to Stack Overflow ; back them up with references or experience... It looks by using head command which fetch me some top rows from a python DataFrame the reflected 's... Are NaN check if entire column is null pandas a spiral curve in Geo-Nodes 3.3 are NA of null values (.. Groups, how to add a new column to an existing DataFrame without paying a fee bad the... In Pandas so far aft article, I will explain how to add a new column to an DataFrame! Prices Dataset I wanted to find any columns/fields that have null values in a engine. Got a boolean same-sized object indicating if the values are NA share within! Bunk bed in a python DataFrame in Geo-Nodes 3.3 is structured and easy to.! Any columns/fields that have null values ( i.e of columns in a,! Other answers in range ( 1000000000000001 ) '' so fast in python 3 two... Pandas Functions for 80 % of your data Science Tasks rooms on offer given the constraints column F are NaN... Not missing any values, but the second column has a NaN value season and your of... Fixed variable set of rational points of an ( almost ) simple algebraic group?...

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