What are the key differences between Pandas' `loc` and `iloc` methods for DataFrame slicing?

How are iloc and loc different?

iloc and loc are two methods for slicing a DataFrame in Pandas. Both methods can be used to select rows and columns, but they differ in how they interpret the input.

loc gets rows (and/or columns) with particular labels.

iloc gets rows (and/or columns) at integer locations.

To demonstrate, consider a series s of characters with a non-monotonic integer index:

>>> s = pd.Series(list("abcdef"), index=[49, 48, 47, 0, 1, 2])
49    a
48    b
47    c
0     d
1     e
2     f

s.loc[0]    # value at index label 0
'd'

s.iloc[0]   # value at index location 0
'a'

s.loc[0:1]  # rows at index labels between 0 and 1 (inclusive)
0    d
1    e

s.iloc[0:1] # rows at index location between 0 and 1 (exclusive)
49    a

Here are some of the differences/similarities between s.loc and s.iloc when passed various objects:

Object	Description	s.loc[Object]	s.iloc[Object]
0	Single item	Value at index label 0 (_the string 'd'_)	Value at index location 0 (_the string 'a'_)
0:1	Slice	Two rows (labels 0 and 1)	One row (first row at location 0)
1:47	Slice with out-of-bounds end	Zero rows (empty Series)	Five rows (location 1 onwards)
1:47:-1	Slice with negative step	three rows (labels 1 back to 47)	Zero rows (empty Series)
[2, 0]	Integer list	Two rows with given labels	Two rows with given locations
s > 'e'	Bool series (indicating which values have the property)	One row (containing 'f')	NotImplementedError
(s>e).values	Bool array	One row (containing 'f')	Same as loc
999	Int object not in index	KeyError	IndexError (out of bounds)
-1	Int object not in index	KeyError	Returns last value in s
lambda x: x.index[3]	Callable applied to series (here returning 3rd item in index)	s.loc[s.index[3]]	s.iloc[s.index[3]]

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