How do I change a single index value in pandas dataframe?
PythonPandasData AnalysisPython Problem Overview
energy.loc['Republic of Korea']
I want to change the value of index from 'Republic of Korea' to 'South Korea'. But the dataframe is too large and it is not possible to change every index value. How do I change only this single value?
Python Solutions
Solution 1 - Python
@EdChum's solution looks good. Here's one using rename, which would replace all these values in the index.
energy.rename(index={'Republic of Korea':'South Korea'},inplace=True)
Here's an example
>>> example = pd.DataFrame({'key1' : ['a','a','a','b','a','b'],
'data1' : [1,2,2,3,nan,4],
'data2' : list('abcdef')})
>>> example.set_index('key1',inplace=True)
>>> example
data1 data2
key1
a 1.0 a
a 2.0 b
a 2.0 c
b 3.0 d
a NaN e
b 4.0 f
>>> example.rename(index={'a':'c'}) # can also use inplace=True
data1 data2
key1
c 1.0 a
c 2.0 b
c 2.0 c
b 3.0 d
c NaN e
b 4.0 f
Solution 2 - Python
You want to do something like this:
as_list = df.index.tolist()
idx = as_list.index('Republic of Korea')
as_list[idx] = 'South Korea'
df.index = as_list
Basically, you get the index as a list, change that one element, and the replace the existing index.
Solution 3 - Python
Try This
df.rename(index={'Republic of Korea':'South Korea'},inplace=True)
Solution 4 - Python
If you have MultiIndex DataFrame, do this:
# input DataFrame
import pandas as pd
t = pd.DataFrame(data={'i1':[0,0,0,0,1,1,1,1,2,2,2,2],
'i2':[0,1,2,3,0,1,2,3,0,1,2,3],
'x':[1.,2.,3.,4.,5.,6.,7.,8.,9.,10.,11.,12.]})
t.set_index(['i1','i2'], inplace=True)
t.sort_index(inplace=True)
# changes index level 'i1' values 0 to -1
t.rename(index={0:-1}, level='i1', inplace=True)
Solution 5 - Python
Here's another good one, using replace on the column.
df.reset_index(inplace=True)
df.drop('index', axis = 1, inplace=True)
df["Country"].replace("Republic of Korea", value="South Korea", inplace=True)
df.set_index("Country", inplace=True)
Solution 6 - Python
Here's another idea based on set_value
df = df.reset_index()
df.drop('index', axis = 1, inplace=True)
index = df.index[df["Country"] == "Republic of Korea"]
df.set_value(index, "Country", "South Korea")
df = df.set_index("Country")
df["Country"] = df.index
Solution 7 - Python
This seems to work too:
energy.index.values[energy.index.tolist().index('Republic of Korea')] = 'South Korea'
No idea though whether this is recommended or discouraged.
Solution 8 - Python
We can use rename function to change row index or column name. Here is the example,
Suppose data frame is like given below,
student_id marks
index
1 12 33
2 23 98
- To change index 1 to 5
we will use axis = 0 which is for row
df.rename({ 1 : 5 }, axis=0)
df refers to data frame variable. So, output will be like
student_id marks
index
5 12 33
2 23 98
- To change column name
we will have to use axis = 1
df.rename({ "marks" : "student_marks" }, axis=1)
so, changed data frame is
student_id student_marks
index
5 12 33
2 23 98