Convert an array of datetimes into an array of strings passing units in Python

To convert an array of datetimes into an array of strings, use the numpy.datetime_as_string() method in Python NumPy. The method returns an array of strings the same shape as the input array. The first parameter is the array of UTC timestamps to format. The "units" parameter sets the datetime unit to change the precision.

Syntax

numpy.datetime_as_string(arr, unit=None, timezone='naive', casting='same_kind')

Parameters

The key parameters are ?

• arr − Array of datetime64 values to convert
• unit − Datetime unit for precision ('Y', 'M', 'D', 'h', 'm', 's', 'ms', etc.)
• timezone − Timezone handling ('naive', 'UTC', or 'local')

Creating a DateTime Array

First, let's create an array of datetime values using np.arange() ?

import numpy as np

# Create an array of datetime with 'M8[m]' dtype (minutes precision)
arr = np.arange('2022-02-20T02:10', 6*60, 60, dtype='M8[m]')

print("Original datetime array:")
print(arr)
print("\nDatatype:", arr.dtype)
print("Shape:", arr.shape)

Original datetime array:
['2022-02-20T02:10' '2022-02-20T03:10' '2022-02-20T04:10'
 '2022-02-20T05:10' '2022-02-20T06:10' '2022-02-20T07:10']

Datatype: datetime64[m]
Shape: (6,)

Converting to String with Different Units

Using Seconds Precision

import numpy as np

arr = np.arange('2022-02-20T02:10', 6*60, 60, dtype='M8[m]')

# Convert to strings with seconds precision
string_array_seconds = np.datetime_as_string(arr, unit='s')

print("With seconds unit:")
print(string_array_seconds)

With seconds unit:
['2022-02-20T02:10:00' '2022-02-20T03:10:00' '2022-02-20T04:10:00'
 '2022-02-20T05:10:00' '2022-02-20T06:10:00' '2022-02-20T07:10:00']

Using Different Units

import numpy as np

arr = np.arange('2022-02-20T02:10', 6*60, 60, dtype='M8[m]')

# Different unit precisions
print("Minutes unit:")
print(np.datetime_as_string(arr, unit='m'))

print("\nHours unit:")
print(np.datetime_as_string(arr, unit='h'))

print("\nDays unit:")
print(np.datetime_as_string(arr, unit='D'))

Minutes unit:
['2022-02-20T02:10' '2022-02-20T03:10' '2022-02-20T04:10'
 '2022-02-20T05:10' '2022-02-20T06:10' '2022-02-20T07:10']

Hours unit:
['2022-02-20T02' '2022-02-20T03' '2022-02-20T04' '2022-02-20T05'
 '2022-02-20T06' '2022-02-20T07']

Days unit:
['2022-02-20' '2022-02-20' '2022-02-20' '2022-02-20' '2022-02-20'
 '2022-02-20']

Common Use Cases

Conclusion

Use numpy.datetime_as_string() to convert datetime arrays to string format. The unit parameter controls precision, allowing you to format timestamps according to your specific requirements.