Introduction to Pandas
Chapter 5: DataFrame operations
DataFrame filtering
Do you only need a subset of the data?
You can filter a DataFrame by selecting a column and applying a condition on it. This will return a Series of True and False values.
For example, you can check whether a Pokemon is of a "Grass" type…
>>> condition_series = (df["Type 1"] == "Grass")
>>> condition_series.head()
Name
Bulbasaur True
Ivysaur True
Venusaur True
VenusaurMega Venusaur True
Charmander False
Name: Type 1, dtype: bool
To return only rows where the condition is True, you can pass the condition into the DataFrame, just like in NumPy.
For example, to show only "Grass" type Pokemons…
>>> filtered_df = df[df["Type 1"] == "Grass"]
>>> filtered_df.head(10)
# Type 1 ... Generation Legendary
Name ...
Bulbasaur 1 Grass ... 1 False
Ivysaur 2 Grass ... 1 False
Venusaur 3 Grass ... 1 False
VenusaurMega Venusaur 3 Grass ... 1 False
Oddish 43 Grass ... 1 False
Gloom 44 Grass ... 1 False
Vileplume 45 Grass ... 1 False
Bellsprout 69 Grass ... 1 False
Weepinbell 70 Grass ... 1 False
Victreebel 71 Grass ... 1 False
A more complicated example (what does it do?)
>>> df[df["Type 1"].isin(["Water", "Fire"])].head(10)
# Type 1 ... Generation Legendary
Name ...
Charmander 4 Fire ... 1 False
Charmeleon 5 Fire ... 1 False
Charizard 6 Fire ... 1 False
CharizardMega Charizard X 6 Fire ... 1 False
CharizardMega Charizard Y 6 Fire ... 1 False
Squirtle 7 Water ... 1 False
Wartortle 8 Water ... 1 False
Blastoise 9 Water ... 1 False
BlastoiseMega Blastoise 9 Water ... 1 False
Vulpix 37 Fire ... 1 False
And another complex one (what does it do?)
>>> filtered_df = df[(df["Type 1"] == "Psychic") &
(df["Generation"] <=3) &
(df["Legendary"] == True)]
>>> filtered_df = filtered_df[["Type 1", "Type 2", "Generation"]]
>>> print(filtered_df)
Type 1 Type 2 Generation
Name
Mewtwo Psychic NaN 1
MewtwoMega Mewtwo X Psychic Fighting 1
MewtwoMega Mewtwo Y Psychic NaN 1
Lugia Psychic Flying 2
DeoxysNormal Forme Psychic NaN 3
DeoxysAttack Forme Psychic NaN 3
DeoxysDefense Forme Psychic NaN 3
DeoxysSpeed Forme Psychic NaN 3