CODEWITHSUNDEEP
pythonpython-3.xpandas
Gupta
Gupta

Reputation: 314

Indexing / slicing methods on data frame

I can see that there are 2/3 ways of indexing. iloc, loc and ix (was there in earlier versions, i guess). While experimenting, I found another way that worked. Wanted clarification, why did it worked? Is loc the default method when user doesnt specify anything?

import pandas as pd
import seaborn as sns
iris = sns.load_dataset("iris")

iris[iris['species']=="setosa"].head() and iris.loc[iris.species == "setosa"].head() gives the same result as

   sepal_length  sepal_width  petal_length  petal_width species
0           5.1          3.5           1.4          0.2  setosa
1           4.9          3.0           1.4          0.2  setosa
2           4.7          3.2           1.3          0.2  setosa
3           4.6          3.1           1.5          0.2  setosa
4           5.0          3.6           1.4          0.2  setosa

I checked iris type is also pandas.core.frame.DataFrame

Upvotes: 1

Views: 41

Answers (1)

MrNobody33
MrNobody33

Reputation: 6483

This two give the same result becasue loc works with either a Boolean Series or a Boolean array.

So when you give the Boolean Series (iris['species']=="setosa")

(iris['species']=="setosa")
0       True
1       True
2       True
3       True
4       True
       ...  
145    False
146    False
147    False
148    False
149    False
Name: species, Length: 150, dtype: bool

Both (iris[iris['species']=="setosa"] and iris.loc[iris.species == "setosa"]) are doing a boolean indexing.

While iloc, works only with a Boolean array, so, to use iloc with the same mask, you can pass the Boolean Series to a numpy array:

iris.iloc[(iris['species']=="setosa").values].head()

Upvotes: 1

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