Pandas astype()

import pandas as pd

# sample DataFrame
data = {'A': ['1', '2', '3'],
        'B': ['4.5', '5.7', '6.8']}

df = pd.DataFrame(data)

# convert entire DataFrame to float
df = df.astype(float)

print(df)

'''
Output

     A    B
0  1.0  4.5
1  2.0  5.7
2  3.0  6.8
'''

astype() Syntax

The syntax of the astype() method in Pandas is:

df.astype(dtype, copy, errors)

astype() Argument

The astype() method takes the following argument:

• dtype - data type or dictionary of column to data type to convert the dataframe into
• copy - whether to return a copy
• errors - controls raising exceptions on invalid data types

astype() Return Value

The astype() method returns a DataFrame with data cast to specified data types.

Example 1: Convert Entire DataFrame to a Single Data Type

import pandas as pd

# sample DataFrame
data = {'A': ['1', '2', '3'],
        'B': ['4.5', '5.7', '6.8']}

df = pd.DataFrame(data)

# convert entire DataFrame to float
df = df.astype(float)

print(df)

Output

     A    B
0  1.0  4.5
1  2.0  5.7
2  3.0  6.8

In this case, we converted the entire DataFrame df to have all its values as float values using the astype() method.

Example 2: Convert Data Type of Single Column

import pandas as pd

# sample DataFrame
data = {'A': ['1', '2', '3'],
        'B': ['4', '5', '6']}

df = pd.DataFrame(data)

# convert column B to float
converted_b = df['B'].astype(float)

print(converted_b)

Output

0    4.0
1    5.0
2    6.0
Name: B, dtype: float64

In this example, we converted the data type of column B. Notice how the astype() function only returns the converted column only.

Example 3: Convert Data Type of Multiple Columns

import pandas as pd

# sample DataFrame
data = {'A': ['1', '2', '3'],
        'B': ['4', '5', '6']}

df = pd.DataFrame(data)

# convert data types of columns A and B
df = df.astype({'A': int, 'B': float})

print(df)

Output

   A    B
0  1  4.0
1  2  5.0
2  3  6.0

In this example, we passed a dictionary in the format {col_name: dtype, ...} to the astype() method to convert data types of multiple columns.