Split pandas dataframe in two if it has more than 10 rows

Question

I have a huge CSV with many tables with many rows  I would like to simply split each dataframe into 2 if it contains more than 10 rows    If true  I would like the first dataframe to contain the first 10 and the rest in the second dataframe    Is there a convenient function for this  I ve looked around but found nothing useful      i e  split dataframe df  2 if  gt  10

User · Answer

A method based on np split   df   pd DataFrame       A   2 4 6 8 10 2 4 6 8 10                           B   10 -10 0 20 -10 10 -10 0 20 -10                           C   4 12 8 0 0 4 12 8 0 0                          D   9 10 0 1 3 np nan np nan np nan np nan np nan     listOfDfs    df loc idx  for idx in np split df index 5     A small function that uses a modulo could take care of cases where the split is not even  e g  np split df index 4  will throw an error     Yes  I am aware that the original question was somewhat more specific than this  However  this is supposed to answer the question in the title

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Below is a simple function implementation which splits a DataFrame to chunks and a few code examples   import pandas as pd  def split dataframe to chunks df  n       df len   len df      count   0     dfs           while True          if count  gt  df len-1              break          start   count         count    n          print   s    s     start  count           dfs append df iloc start   count       return dfs     Create a DataFrame with 10 rows df   pd DataFrame  i for i in range 10       Split the DataFrame to chunks of maximum size 2 split df to chunks of 2   split dataframe to chunks df  2  print  len i  for i in split df to chunks of 2     prints   2  2  2  2  2     Split the DataFrame to chunks of maximum size 3 split df to chunks of 3   split dataframe to chunks df  3  print  len i  for i in split df to chunks of 3     prints  3  3  3  1

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If you have a large data frame and need to divide into a variable number of sub data frames rows  like for example each sub dataframe has a max of 4500 rows  this script could help   max rows   4500 dataframes      while len df   gt  max rows      top   df  max rows      dataframes append top      df   df max rows   else      dataframes append df    You could then save out these data frames   for    frame in enumerate dataframes       frame to csv str      csv   index False    Hope this helps someone

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I used a List Comprehension to cut a huge DataFrame into blocks of 100 000   size   100000 list of dfs    df loc i i size-1    for i in range 0  len df  size     or as generator   list of dfs    df loc i i size-1    for i in range 0  len df  size

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def split and save df df  name  size  output dir               Split a df and save each chunk in a different csv file       Parameters          df   pandas df to be splitted         name   name to give to the output file         size   chunk size         output dir   directory where to write the divided df             import os     for i in range 0  df shape 0  size           start    i         end      min i size-1  df shape 0            subset   df loc start end           output path   os path join output dir f  name   start   end  csv           print f Going to write into  output path            subset to csv output path          output size   os stat output path  st size         print f Wrote  output size  bytes

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There is no specific convenience function   You d have to do something like   first ten   pd DataFrame   rest   pd DataFrame    if df shape 0   gt  10    len df   gt  10 would also work     first ten   df  10      rest   df 10

User · Answer

This will return the split DataFrames if the condition is met  otherwise return the original and None  which you would then need to handle separately   Note that this assumes the splitting only has to happen one time per df and that the second part of the split  if it is longer than 10 rows  meaning that the original was longer than 20 rows   is OK   df new1  df new2   df  10      df 10      if len df   gt  10 else df  None   Note you can also use df head 10  and df tail len df  - 10  to get the front and back according to your needs  You can also use various indexing approaches  you can just provide the first dimensions index if you want  such as df  10  instead of df  10      though I like to code explicitly about the dimensions you are taking   You can can also use df iloc and df ix to index in similar ways   Be careful about using df loc however  since it is label-based and the input will never be interpreted as an integer position   loc would only work  accidentally  in the case when you happen to have index labels that are integers starting at 0 with no gaps   But you should also consider the various options that pandas provides for dumping the contents of the DataFrame into HTML and possibly also LaTeX to make better designed tables for the presentation  instead of just copying and pasting   Simply Googling how to convert the DataFrame to these formats turns up lots of tutorials and advice for exactly this application

User · Answer

You can use the DataFrame head and tail methods as syntactic sugar instead of slicing loc here  I use a split size of 3  for your example use headSize 10  def split df  headSize        hd   df head headSize      tl   df tail len df -headSize      return hd  tl  df   pd DataFrame       A   2 4 6 8 10 2 4 6 8 10                           B   10 -10 0 20 -10 10 -10 0 20 -10                           C   4 12 8 0 0 4 12 8 0 0                          D   9 10 0 1 3 np nan np nan np nan np nan np nan       Split dataframe into top 3 rows  first  and the rest  second  first  second   split df  3

User · Answer

The method based on list comprehension and groupby  which stores all the split dataframes in a list variable and can be accessed using the index   Example   ans    pd DataFrame y  for x  y in DF groupby  column name   as index False      ans 0  ans 0  column name

[python] Split pandas dataframe in two if it has more than 10 rows

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