How to Check the Dtype of Column(s) in Pandas DataFrame

John D K -

To check the dtypes of single or multiple columns in Pandas you can use:

df.dtypes

Let's see other useful ways to check the dtypes in Pandas.

Step 1: Create sample DataFrame

To start, let's say that you have the date from earthquakes:

Date Time Depth Magnitude Type Type Magnitude Depth_int
1965-01-02 00:00:00+00:00 13:44:18 131.6 MW Earthquake 6.0 131
1965-01-04 00:00:00+00:00 11:29:49 80.0 MW Earthquake 5.8 80
1965-01-05 00:00:00+00:00 18:05:58 20.0 MW Earthquake 6.2 20
1965-01-08 00:00:00+00:00 18:49:43 15.0 MW Earthquake 5.8 15
1965-01-09 00:00:00+00:00 13:32:50 15.0 MW Earthquake 5.8 15

Data is available from Kaggle: Significant Earthquakes, 1965-2016.

How to read and convert Kaggle data to Pandas DataFrame: How to Search and Download Kaggle Dataset to Pandas DataFrame

Step 2: Get dtypes for all columns in DataFrame

To get dtypes details for the whole DataFrame you can use attribute - dtypes:

df.dtypes

the result is:

Date              datetime64[ns, UTC]
Time                           object
Depth                         float64
Magnitude Type                 object
Type                           object
Magnitude                     float64
Depth_int                       int64
dtype: object

we can see several different types like:

  • datetime64[ns, UTC] - it's used for dates; explicit conversion may be needed in some cases
  • float64 / int64 - numeric data
  • object - strings and other

Step 3: Short explanation of dtypes in Pandas

Let's briefly cover some dtypes and their usage with simple examples. Table of the most used dtypes in Pandas:

Pandas dtype Data Type Description Example Creation
bool bool Boolean values – True or False True pd.BooleanDtype()
category NA Limited list of values (can be fixed) [‘red’, ‘blue’] pd.Categorical([1, 2, 3, 1, 2, 3])
datetime64 datetime Datetime (conversion is needed) 2020-11-16 22:50:18.092888+0000 to_datetime(df['date'])
float64 float Floating point numbers 80.5 df.astype('float64')
int64 int Integer numbers 8 df.astype('int64')
object strings String, text and other Red Pandas
timedelta timedelta Duration between two dates or times 0 days 00:00:00.000000001 pd.Timedelta(42, unit='ns')

More information about them can be found on this link: Pandas User Guide dtypes.

Pandas offers a wide range of features and methods in order to read, parse and convert between different dtypes. The most popular conversion methods are:

  • to_datetime(df['date'])
  • to_timedelta(df['timdelta'])
  • to_numeric(df['amount'])
  • df['amount'].astype('int32')

Step 4: Check if column is numeric, datetime, categorical etc

In this step we are going to see how we can check if a given column is numerical or categorical.

For this purpose Pandas offers a bunch of methods like:

  • is_string_dtype
  • is_dict_like
  • is_list_like
  • is_numeric_dtype
  • is_datetime64_dtype

To find all methods you can check the official Pandas docs: pandas.api.types.is_datetime64_any_dtype

To check if a column has numeric or datetime dtype we can:

from pandas.api.types import is_numeric_dtype
is_numeric_dtype(df['Depth_int'])

result:

True

for datetime exists several options like: is_datetime64_ns_dtype or is_datetime64_any_dtype:

from pandas.api.types import is_datetime64_any_dtype
is_datetime64_any_dtype(df['Date'])

result:

True

Step 5: List all numeric/datetime columns in Pandas DataFrame

If you like to list only numeric/datetime or other type of columns in a DataFrame you can use method select_dtypes:

including

df.select_dtypes(include=['float64']).columns

result of the operation:

Index(['Depth', 'Magnitude'], dtype='object')

excluding columns by dtype:

df.select_dtypes(exclude=['float64','datetime']).columns

result:

Index(['Date', 'Time', 'Magnitude Type', 'Type', 'Depth_int'], dtype='object')

Step 6: Filter columns by dtype and name in Pandas DataFrame

As an alternative solution you can construct a loop over all columns. Then you can check the dtype and the name of the column.

Below we are listing all numeric column which name has word 'Depth':

from pandas.api.types import is_numeric_dtype

for col in df.columns:
    if is_numeric_dtype(df[col]) and 'Depth' in col:
          print(col)

As a result you will get a list of all numeric columns:

Depth
Depth_int

Instead of printing their names you can do something.

Step 7: Apply function on numeric columns only

To apply function to numeric or datetime columns only you can use the method select_dtypes in combination with apply.

The function below will iterate over all numeric columns and double the value:

def double_n(x):
    return x *

df.select_dtypes(include=['float64']).apply(double_n)

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