rename elements in a column of a data frame using pandas
Question:
Using pandas:
df = pd.DataFrame({'n':['d','a','b','c','c','a','d','b'], 'v':[1,2,1,2,2,1,1,1]})
How can I rename the elements in df.n, such that a changes to x, b to y, c to w and d to z, resulting in:
n v
0 z 1
1 x 2
2 y 1
3 w 2
...
Answers:
You can pass a dictionary of replacement values into the Series replace method:
In [11]: df['n'].replace({'a': 'x', 'b': 'y', 'c': 'w', 'd': 'z'})
Out[11]:
0 z
1 x
2 y
3 w
4 w
5 x
6 z
7 y
Name: n, dtype: object
In [12]: df['n'] = df['n'].replace({'a': 'x', 'b': 'y', 'c': 'w', 'd': 'z'})
You can also use the below one:
df['n'].replace(['a', 'b', 'c', 'd'], ['x', 'y', 'w', 'z'])
This will replace all the a with x, b with y, c with w, and d with z. Note: if you pass two lists they both must be the same length.
Slightly Modified from above:
movies[‘price’].replace({"$":"low","$$":"moderate","$$$":"high","$$$$":"very high"},inplace=True)
"Use inplace =True " otherwise dataframe won’t be updated.
Using pandas:
df = pd.DataFrame({'n':['d','a','b','c','c','a','d','b'], 'v':[1,2,1,2,2,1,1,1]})
How can I rename the elements in df.n, such that a changes to x, b to y, c to w and d to z, resulting in:
n v
0 z 1
1 x 2
2 y 1
3 w 2
...
You can pass a dictionary of replacement values into the Series replace method:
In [11]: df['n'].replace({'a': 'x', 'b': 'y', 'c': 'w', 'd': 'z'})
Out[11]:
0 z
1 x
2 y
3 w
4 w
5 x
6 z
7 y
Name: n, dtype: object
In [12]: df['n'] = df['n'].replace({'a': 'x', 'b': 'y', 'c': 'w', 'd': 'z'})
You can also use the below one:
df['n'].replace(['a', 'b', 'c', 'd'], ['x', 'y', 'w', 'z'])
This will replace all the a with x, b with y, c with w, and d with z. Note: if you pass two lists they both must be the same length.
Slightly Modified from above:
movies[‘price’].replace({"$":"low","$$":"moderate","$$$":"high","$$$$":"very high"},inplace=True)
"Use inplace =True " otherwise dataframe won’t be updated.