5 Best Ways to Convert pandas Timedelta to NumPy timedelta64

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💡 Problem Formulation: Converting time differences into a uniform format is critical in data analysis. In Python, the pandas library represents time differences using Timedelta objects, while NumPy uses timedelta64. This article will walk you through different methods to convert a pandas Timedelta to a NumPy timedelta64 object. For instance, if you have a pandas Timedelta of ‘2 days 00:00:00’, the goal is to convert it to a NumPy timedelta64 value in a specified time unit.

Method 1: Using to_timedelta64() Method

This method directly converts a pandas Timedelta object to a NumPy timedelta64 object using the to_timedelta64 method which is straightforward and efficient for individual Timedelta objects.

Here’s an example:

import pandas as pd

# Creating a pandas Timedelta
pandas_td = pd.Timedelta(days=2)

# Converting to NumPy timedelta64
numpy_td64 = pandas_td.to_timedelta64()

print(numpy_td64)

Output:

172800000000000 nanoseconds

This code snippet demonstrates the conversion of a pandas Timedelta representing 2 days to its equivalent NumPy timedelta64 in nanoseconds. The to_timedelta64() method is explicitly called on the pandas Timedelta object to perform the conversion.

Method 2: Using NumPy’s timedelta64() Constructor

NumPy’s timedelta64 constructor can create a timedelta64 object by directly converting the string representation of the pandas Timedelta.

Here’s an example:

import pandas as pd
import numpy as np

# Creating a pandas Timedelta
pandas_td = pd.Timedelta('1 days 06:00:00')

# Converting to NumPy timedelta64 using the constructor
numpy_td64 = np.timedelta64(pandas_td)

print(numpy_td64)

Output:

1 days +06:00:00

This snippet constructs a pandas Timedelta and converts it into a NumPy timedelta64 object using the NumPy timedelta64 constructor. This method ensures that the converted time retains its days and time structure.

Method 3: Using astype() on a pandas Series

When dealing with a Series of Timedelta objects in pandas, the astype() method is utilized to cast the entire Series to timedelta64 with the desired time unit.

Here’s an example:

import pandas as pd

# Creating a pandas Series of Timedelta objects
timedeltas = pd.Series([pd.Timedelta(days=i) for i in range(3)])

# Converting the entire Series to NumPy timedelta64
numpy_td64_series = timedeltas.astype('timedelta64[ms]')

print(numpy_td64_series)

Output:

0             0
1       86400000
2      172800000
dtype: timedelta64[ms]

In this example, a Series of pandas Timedelta objects is converted to a Series of NumPy timedelta64 in milliseconds using the astype() method. This method is particularly useful for batch processing in pandas data structures.

Method 4: Employing pd.to_timedelta() Method

The pd.to_timedelta() method can be used to convert multiple formats of time differences, including lists or arrays of strings, to pandas Timedelta objects, which in turn can be converted to timedelta64 using the aforementioned methods.

Here’s an example:

import pandas as pd
import numpy as np

# Create an array of string time differences
time_diffs = ['1 days', '2 days', '3 days']

# Convert to pandas Timedelta objects
pd_timedeltas = pd.to_timedelta(time_diffs)

# Convert to NumPy timedelta64 objects
numpy_td64_array = np.array(pd_timedeltas, dtype='timedelta64[h]')

print(numpy_td64_array)

Output:

[24 48 72] hours

This example illustrates how an array of string time differences is first converted into pandas Timedelta objects and then cast to a NumPy array of timedelta64[h], highlighting the flexibility of using pd.to_timedelta() for initial conversion.

Bonus One-Liner Method 5: Using view() Function

When the demand is to quickly convert a pandas Timedelta to NumPy timedelta64 without specifying units, the view() function is convenient as it can do the conversion in a single line of code.

Here’s an example:

import pandas as pd

# Creating a pandas Timedelta
pandas_td = pd.Timedelta('5 days 12:00:00')

# One-liner conversion to NumPy timedelta64
numpy_td64 = pandas_td.view('timedelta64')

print(numpy_td64)

Output:

480000000000 nanoseconds

This one-liner uses the view() function on a pandas Timedelta to obtain its representation as a NumPy timedelta64. This method is a convenient shortcut for direct conversions without explicit type or unit specification.

Summary/Discussion

  • Method 1: to_timedelta64() Method. Most straightforward for individual objects. Limited to scalar conversions.
  • Method 2: NumPy’s timedelta64() Constructor. Directly uses the Timedelta’s string representation for conversion. May not provide control over units.
  • Method 3: Using astype() on a pandas Series. Best for converting an entire Series of Timedeltas. Requires pandas Series structure.
  • Method 4: Employing pd.to_timedelta() Method. Offers flexibility for converting diverse time formattings before casting to NumPy. Extra step for conversion to NumPy.
  • Method 5: Using view() Function. Fast, concise one-liner. Not explicit about units and does not allow for unit specification.