Python Replace Whole Values in Dataframe String and Not Substrings

Question

I am trying to replace strings in a dataframe if the whole string equals another string. I do not want to replace substrings.

So:

If I have df:

 Index  Name       Age
   0     Joe        8
   1     Mary       10
   2     Marybeth   11

and I want to replace "Mary" when the whole string matches "Mary" with "Amy" so I get

 Index  Name       Age
   0     Joe        8
   1     Amy        10
   2     Marybeth   11

I'm doing the following:

df['Name'] = df['Name'].apply(lambda x: x.replace('Mary','Amy'))

My understanding from searching around is that the defaults of replace set regex=False and replace should look for the whole value in the dataframe to be "Mary". Instead I'm getting this result:

 Index  Name       Age
   0     Joe        8
   1     Amy        10
   2     Amybeth   11

What am I doing wrong?

Answer 1

replace + dict is the way to go (With DataFrame, you are using Series.str.replace)

df['Name'].replace({'Mary':'Amy'})
Out[582]: 
0         Joe
1         Amy
2    Marybeth
Name: Name, dtype: object
df['Name'].replace({'Mary':'Amy'},regex=True)
Out[583]: 
0        Joe
1        Amy
2    Amybeth
Name: Name, dtype: object

Notice they are different

Series: https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.str.replace.html

DataFrame: https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.replace.html