Difference between isin, str.contains and if condition?

Question

I am generally confused as to if I want to filter a dataframe column items with something, should isin or .str.contains or if "aa" in df["column"] is used?

Kindly tell me which of them are used in different cases ?

Answer 1

isin

Use isin if you want to check the occurrence of one of multiple strings in the values of a Series:

import pandas as pd                                                                                                      
things = pd.Series(['apple', 'banana', 'house', 'car'])                                                                                                                              
fruits = ['apple', 'banana', 'kiwi']                                                                                                                                            
things.isin(fruits)

Output:

0     True
1     True
2    False
3    False
dtype: bool

.str.contains

.str.contains does the same but only for one string and it also matches parts of strings.

things.str.contains('apple')

Output:

0     True
1    False
2    False
3    False
dtype: bool

things.str.contains('app')

Output:

0     True
1    False
2    False
3    False
dtype: bool

in

A in series checks whether A is in the index of the pd.Series:

"apple" in things                                                                                                                                                              
# Output: False

Our things series has no 'apple' in its indices, it is quickly clear why:

> things
0     apple
1    banana
2     house
3       car
dtype: object

The first column describes the index, so we can check it:

0 in things                                                                                                                                                              
# Output: True