How to convert pandas dataframe columsn from float64 to object dataype

Question

Need to convert pandas dataframe columsn from float64 to object datatype with mentioning the column name.

Input Data

customer_number|email_type|email|phone_type|phone
123|ABC|Primary|abc.def@dd.edu|Mobile|+12345678

Data type :

Customer_number       int64
first_name           object
email_type           object
email                object
phone_type           object
phone               float64

Expected Output Data type

Data type :
Customer_number       int64
first_name           object
email_type           object
email                object
phone_type           object
phone                object

Code

df = pd.read_csv("filename.csv",sep="|")
df['phone'] = df['phone'].astype(str).str.replace('\.0', '')

I don't want to mentioned columns name in code. It should be work for all the columns which has float64 datatype.