[FIXED] Pandas: convert object to str

Issue

I have the following dataframe:

    R_fighter       B_fighter           win_by                  last_round  Referee         date            Winner
0   Adrian Yanez    Gustavo Lopez       KO/TKO                  3           Chris Tognoni   March 20, 2021  Adrian Yanez
1   Trevin Giles    Roman Dolidze       Decision - Unanimous    3           Herb Dean       March 20, 2021  Trevin Giles
2   Tai Tuivasa     Harry Hunsucker     KO/TKO                  1           Herb Dean       March 20, 2021  Tai Tuivasa
3   Cheyanne Buys   Montserrat Conejo   Decision - Unanimous    3           Mark Smith      March 20, 2021  Montserrat Conejo
4   Marion Reneau   Macy Chiasson       Decision - Unanimous    3           Mark Smith      March 20, 2021  Macy Chiasson

I'm trying to convert the type of the column win_by from object to str.
I use .astype() as suggested here How to convert column with dtype as object to string in Pandas Dataframe:

UFC_db['win_by'] = UFC_db['win_by'].astype('|S')

but nothing changed:

<class 'pandas.core.frame.DataFrame'>
RangeIndex: 6012 entries, 0 to 6011
Data columns (total 7 columns):
 #   Column      Non-Null Count  Dtype 
---  ------      --------------  ----- 
 0   R_fighter   6012 non-null   object
 1   B_fighter   6012 non-null   object
 2   win_by      6012 non-null   object
 3   last_round  6012 non-null   object
 4   Referee     6012 non-null   object
 5   date        6012 non-null   object
 6   Winner      6012 non-null   object
dtypes: object(7)
memory usage: 328.9+ KB

I also tried

UFC_db['win_by'] = UFC_db['win_by'].astype('str')

UFC_db['win_by'] = UFC_db['win_by'].astype(str)

and

UFC_db['win_by'] = UFC_db['win_by'].astype('str',errors ="ignore")

as suggested here Python - pandas column type casting with "astype" is not working

but still nothing changed

Solution

I realize that object is not a problem, instead is the type that pandas use for string or mixed types (https://pbpython.com/pandas_dtypes.html). More precisely:

Pandas dtype	Python type	NumPy type	Usage
object	str or mixed	string_, unicode_, mixed types	Text or mixed numeric and non-numeric values
int64	int	int_, int8, int16, int32, int64, uint8, uint16, uint32, uint64	Integer numbers
float64	float	float_, float16, float32, float64	Floating point numbers

Infact if I print the type of a single cell it gives me str

type(UFC_db.at[0,'Referee'])

str

and as a string I can change it with another string

UFC_db.at[0,'Referee'] = 'XXXXXX'
UFC_db.at[0,'Referee']

'XXXXXX'

Answered By - paolopazzo