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Change Data Type for one or more columns in Pandas Dataframe

  • Last Updated : 26 Dec, 2018

Let’s see the different ways of changing Data Type for one or more columns in Pandas Dataframe.

Method #1: Using DataFrame.astype()

We can pass any Python, Numpy or Pandas datatype to change all columns of a dataframe to that type, or we can pass a dictionary having column names as keys and datatype as values to change type of selected columns.




# importing pandas as pd
import pandas as pd
  
# sample dataframe
df = pd.DataFrame({
    'A': [1, 2, 3, 4, 5],
    'B': ['a', 'b', 'c', 'd', 'e'],
    'C': [1.1, '1.0', '1.3', 2, 5] })
  
# converting all columns to string type
df = df.astype(str)
print(df.dtypes)

Output:

 




# importing pandas as pd
import pandas as pd
  
# sample dataframe
df = pd.DataFrame({
    'A': [1, 2, 3, 4, 5],
    'B': ['a', 'b', 'c', 'd', 'e'],
    'C': [1.1, '1.0', '1.3', 2, 5] })
  
# using dictionary to convert specific columns
convert_dict = {'A': int,
                'C': float
               }
  
df = df.astype(convert_dict)
print(df.dtypes)

Output:

 
Method #2: Using DataFrame.apply()



We can pass pandas.to_numeric, pandas.to_datetime and pandas.to_timedelta as argument to apply() function to change the datatype of one or more columns to numeric, datetime and timedelta respectively.




# importing pandas as pd
import pandas as pd
  
# sample dataframe
df = pd.DataFrame({
    'A': [1, 2, 3, '4', '5'],
    'B': ['a', 'b', 'c', 'd', 'e'],
    'C': [1.1, '2.1', 3.0, '4.1', '5.1'] })
  
# using apply method
df[['A', 'C']] = df[['A', 'C']].apply(pd.to_numeric)
print(df.dtypes)

Output:

 
Method #3: Using DataFrame.infer_objects()
This method attempts soft-conversion by inferring data type of ‘object’-type columns. Non-object and unconvertible columns are left unchanged.




# importing pandas as pd
import pandas as pd
  
# sample dataframe
df = pd.DataFrame({
    'A': [1, 2, 3, 4, 5],
    'B': ['a', 'b', 'c', 'd', 'e'],
    'C': [1.1, 2.1, 3.0, 4.1, 5.1]
     }, dtype ='object')
  
# converting datatypes
df = df.infer_objects()
print(df.dtypes)

Output:

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