Python - Slice Dataframe in several smaller dataframes

Question

I have a dataframe with 3000 rows, sorted by date, and 5 columns.

I need to slice this dataframe in several ones, of 251 days, using a loop. So the first one will have from day 1 to day 251, the 2nd one from day 2 to 252, and so on.

Then, I want to save it, so then I can iterate a function over it.

Can you please help me? Thanks in advance.

[SOLVED]

Axel Puig · Accepted Answer · 2018-12-06 00:33:03Z

2

You can create a list of these dataframes this way:

step = 250
dataframe_list = [dataframe[i:i + step] for i in range(len(dataframe) - step)]

if you want to use this in a loop only once, you can use a generator to use less memory.

dataframe_generator = (dataframe[i:i + step] for i in range(len(dataframe) - step))

edited Dec 6, 2018 at 0:33

answered Dec 5, 2018 at 22:50

Axel Puig

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4 Comments

Bernardo Falcao Over a year ago

Hi @Axel, Thank you for your help. I tried your suggestion, but it happens to create list from row 1 to 249 and then from 250 to 499, instead of 1 to 249, 2 to 250, 3 to 251 and so on. Here's what I wrote with your suggestion: step = 250 prices_list = [prices[i:i + step] for i in range(0, len(prices), step)]

Axel Puig Over a year ago

Oh sorry. Corrected.

Bernardo Falcao Over a year ago

Perfect, it worked. Thank you. Is there any way to refer directly to, for instance, the 45th iteration?

Axel Puig Over a year ago

With the first solution, of course: dataframe_list[45], but with the generator, it is not possible (or you have to do a loop with the next function, very inefficient). If you need it, you can just write dataframe[45:45 + step]

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