How to use a string to set iloc in pandas

Question

I understand the general usage of iloc as follows.

import pandas as pd
df = pd.DataFrame([[1,2,3,4,5],[4,5,6,4,5],[7,8,9,4,5],[10,11,12,4,5]])
df_ = df.iloc[:, 1:4]

On the other hand, although it is a limited usage, is it possible to set iloc using a string?

Below is pseudo code that does not work properly but is what I would like to do.

import pandas as pd
df = pd.DataFrame([[1,2,3,4,5],[4,5,6,4,5],[7,8,9,4,5],[10,11,12,4,5]])
df.columns = ["money","job","fruits","animals","height"]
tests = ["1:2","2:3", "1:4"]
for i in tests:
    print(df.iloc[:,i])

Is there a better way to split the string into "start_col" and "end_col" using a function?

Asked By: x H

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Source

Answer 1

You an just create a converter function:

import pandas as pd
df = pd.DataFrame([[1,2,3,4,5],[4,5,6,4,5],[7,8,9,4,5],[10,11,12,4,5]])
ranges = ["1:2", "2:3", "1:4"]


def as_int_range(ranges):
    return [i for rng in ranges for i in range(*map(int, rng.split(':')))]


df.iloc[as_int_range(ranges),:]

    0   1   2  3  4
1   4   5   6  4  5
2   7   8   9  4  5
1   4   5   6  4  5
2   7   8   9  4  5
3  10  11  12  4  5

Answered By: Andreas

Answer 2

iloc[ ] is for slicing numeric data. For String slicing, you can use loc[ ] like you have used iloc[ ] for numbers. Here is the official pandas documentation for implementing loc[ ] https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.loc.html

Answered By: Anish Khatiwada

Answer 3

I didn’t mention it in my original question.
I wrote a program that supports examples like ["1:3, 4"].

import pandas as pd

df = pd.DataFrame([[1,2,3,4,5],[4,5,6,4,5],[7,8,9,4,5],[10,11,12,4,5]])
df.columns = ["a", "b", "c" , "d", "e"]

def args_to_list(string):
    strings = string.split(",")
    column_list = []
    for each_string in strings:
        each_string = each_string.strip()
        if ":" in each_string:
            start_ , end_  = each_string.split(":")
            for i in range(int(start_), int(end_)):
                column_list.append(i)
        else:
            column_list.append(int(each_string))

    return column_list
    
tests = ["1:2", "1,2,3,4", "1:2,3", "1,2:3,4"]

for i in tests:
    list_ =args_to_list(i)
    print(list_)
    print(df.iloc[:, list_])
    print(list_)

Answered By: x H

How to use a string to set iloc in pandas

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