How to construct a timedelta object from a simple string

Question

I'm writing a function that needs to parse string to a timedelta. The user must enter something like "32m" or "2h32m", or even "4:13" or "5hr34m56s"... Is there a library or something that has this sort of thing already implemented?

Answer 1

To me the most elegant solution, without having to resort to external libraries such as dateutil or manually parsing the input, is to use datetime's powerful strptime string parsing method.

from datetime import datetime, timedelta
# we specify the input and the format...
t = datetime.strptime("05:20:25","%H:%M:%S")
# ...and use datetime's hour, min and sec properties to build a timedelta
delta = timedelta(hours=t.hour, minutes=t.minute, seconds=t.second)

After this you can use your timedelta object as normally, convert it to seconds to make sure we did the correct thing etc.

print(delta)
assert(5*60*60+20*60+25 == delta.total_seconds())

Answer 2

I had a bit of time on my hands yesterday, so I developed @virhilo's answer into a Python module, adding a few more time expression formats, including all those requested by @priestc.

Source code is on github (MIT License) for anybody that wants it. It's also on PyPI:

pip install pytimeparse

Returns the time as a number of seconds:

>>> from pytimeparse.timeparse import timeparse
>>> timeparse('32m')
1920
>>> timeparse('2h32m')
9120
>>> timeparse('4:13')
253
>>> timeparse('5hr34m56s')
20096
>>> timeparse('1.2 minutes')
72

Answer 3

For the first format (5hr34m56s), you should parse using regular expressions

Here is re-based solution:

import re
from datetime import timedelta


regex = re.compile(r'((?P<hours>\d+?)hr)?((?P<minutes>\d+?)m)?((?P<seconds>\d+?)s)?')


def parse_time(time_str):
    parts = regex.match(time_str)
    if not parts:
        return
    parts = parts.groupdict()
    time_params = {}
    for name, param in parts.items():
        if param:
            time_params[name] = int(param)
    return timedelta(**time_params)


>>> from parse_time import parse_time
>>> parse_time('12hr')
datetime.timedelta(0, 43200)
>>> parse_time('12hr5m10s')
datetime.timedelta(0, 43510)
>>> parse_time('12hr10s')
datetime.timedelta(0, 43210)
>>> parse_time('10s')
datetime.timedelta(0, 10)
>>> 

Answer 4

I wanted to input just a time and then add it to various dates so this worked for me:

from datetime import datetime as dtt

time_only = dtt.strptime('15:30', "%H:%M") - dtt.strptime("00:00", "%H:%M")

Answer 5

I've modified virhilo's nice answer with a few upgrades:

• added a assertion that the string is a valid time string
• replace the "hr" hour-indicator with "h"
• allow for a "d" - days indicator
• allow non-integer times (e.g. 3m0.25s is 3 minutes, 0.25 seconds)

.

import re
from datetime import timedelta


regex = re.compile(r'^((?P<days>[\.\d]+?)d)?((?P<hours>[\.\d]+?)h)?((?P<minutes>[\.\d]+?)m)?((?P<seconds>[\.\d]+?)s)?$')


def parse_time(time_str):
    """
    Parse a time string e.g. (2h13m) into a timedelta object.

    Modified from virhilo's answer at https://stackoverflow.com/a/4628148/851699

    :param time_str: A string identifying a duration.  (eg. 2h13m)
    :return datetime.timedelta: A datetime.timedelta object
    """
    parts = regex.match(time_str)
    assert parts is not None, "Could not parse any time information from '{}'.  Examples of valid strings: '8h', '2d8h5m20s', '2m4s'".format(time_str)
    time_params = {name: float(param) for name, param in parts.groupdict().items() if param}
    return timedelta(**time_params)

Answer 6

If Pandas is already in your dependencies, it does this pretty well:

>>> import pandas as pd
>>> pd.Timedelta('5hr34m56s')
Timedelta('0 days 05:34:56')

>>> pd.Timedelta('2h32m')
Timedelta('0 days 02:32:00')

>>> pd.Timedelta('5hr34m56s')
Timedelta('0 days 05:34:56')

>>> # It is pretty forgiving:
>>> pd.Timedelta('2 days 24:30:00 10 sec')
Timedelta('3 days 00:30:10')

To convert to datetime.timedelta if you prefer that type:

>>> pd.Timedelta('1 days').to_pytimedelta()
datetime.timedelta(1)

Unfortunately this does not work though:

>>> pd.Timedelta('4:13')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pandas\_libs\tslibs\timedeltas.pyx", line 1217, in 
pandas._libs.tslibs.timedeltas.Timedelta.__new__
  File "pandas\_libs\tslibs\timedeltas.pyx", line 454, in 
pandas._libs.tslibs.timedeltas.parse_timedelta_string
ValueError: expected hh:mm:ss format

Pandas actually has pretty extensive date and time tools even though that is not its main purpose.

To install Pandas:

# If you use pip
pip install pandas

# If you use conda
conda install pandas

Answer 7

Django comes with the utility function parse_duration(). From the documentation:

Parses a string and returns a datetime.timedelta.

Expects data in the format "DD HH:MM:SS.uuuuuu" or as specified by ISO 8601 (e.g. P4DT1H15M20S which is equivalent to 4 1:15:20) or PostgreSQL's day-time interval format (e.g. 3 days 04:05:06).

Answer 8

Use isodate library to parse ISO 8601 duration string. For example:

isodate.parse_duration('PT1H5M26S')

Also see Is there an easy way to convert ISO 8601 duration to timedelta?

Answer 9

if you want to use : as separator, I use this function:

import re
from datetime import timedelta

def timedelta_parse(value):
    """
    convert input string to timedelta
    """
    value = re.sub(r"[^0-9:.]", "", value)
    if not value:
        return

    return timedelta(**{key:float(val)
                        for val, key in zip(value.split(":")[::-1], 
                                            ("seconds", "minutes", "hours", "days"))
               })

Examples:

In [4]: timedelta_parse("1:0:0:1")
Out[4]: datetime.timedelta(days=1, seconds=1)

In [5]: timedelta_parse("123.5")
Out[5]: datetime.timedelta(seconds=123, microseconds=500000)

In [6]: timedelta_parse("1:6:34:9.983")
Out[6]: datetime.timedelta(days=1, seconds=23649, microseconds=983000)

In [8]: timedelta_parse("23:45:00")
Out[8]: datetime.timedelta(seconds=85500)

Answer 10

If you use Python 3 then here's updated version for Hari Shankar's solution, which I used:

from datetime import timedelta
import re

regex = re.compile(r'(?P<hours>\d+?)/'
                   r'(?P<minutes>\d+?)/'
                   r'(?P<seconds>\d+?)$')

def parse_time(time_str):
    parts = regex.match(time_str)
    if not parts:
        return
    parts = parts.groupdict()
    print(parts)
    time_params = {}
    for name, param in parts.items():
        if param:
            time_params[name] = int(param)
    return timedelta(**time_params)

Answer 11

import re
from datetime import timedelta

class InvalidTimeString(Exception):
    """Exception raised when the input string is not a valid time string."""

_TIME_REGEX = re.compile(r'((?P<hours>\d+?)hr)|((?P<minutes>\d+?)m)|((?P<seconds>\d+?)s)')

def parse_time(time_str: str) -> timedelta | None:
    """
    Parse a time string into a timedelta object.

    Args:
        time_str (str): The time string to parse. This can include hours ("Xhr"), minutes ("Ym"), and seconds ("Zs").
            Each component is optional and can appear in any order, but they should be separated by non-numeric characters.

    Returns:
        timedelta: A timedelta object representing the time in the input string.

    Raises:
        InvalidTimeString: If the input string is not a valid time string.

    Usage:
    >>> parse_time('12hr5m10s')
    datetime.timedelta(seconds=43510)
    >>> parse_time('12hr')
    datetime.timedelta(seconds=43200)
    >>> parse_time('12hr10s')
    datetime.timedelta(seconds=43210)
    >>> parse_time('12hr5m10s')
    datetime.timedelta(seconds=43510)
    >>> parse_time('5m10s12hr')
    datetime.timedelta(seconds=43510)
    """
    time_params = {"hours": 0, "minutes": 0, "seconds": 0}
    matches = _TIME_REGEX.finditer(time_str)
    if not matches:
        raise InvalidTimeString(f"'{time_str}' is not a valid time string")

    for match in matches:
        match_dict = match.groupdict()
        for name, param in match_dict.items():
            if param:
                time_params[name] = int(param)

    return timedelta(**time_params)

The parse_time function is designed to parse a time string into a Python timedelta object. The input time string can include hours ("Xhr"), minutes ("Ym"), and seconds ("Zs") in any order. Each component is optional and can be separated by non-numeric characters.

The function begins by defining a regular expression that is capable of matching these time string components. This regular expression includes named groups for hours, minutes, and seconds, which makes it easier to extract these values later.

Next, the function uses the finditer method of the regular expression to find all matches in the input string. This method returns an iterator yielding match objects for every non-overlapping match of the regular expression pattern in the string.

The function then iterates over each match, converting the match object into a dictionary using the groupdict method. This method returns a dictionary containing all the named groups found in the match, with the group names as the keys and the matched strings as the values.

For each named group in the dictionary, the function checks if the group has a value. If it does, the function converts this value into an integer and stores it in the time_params dictionary under the appropriate key (hours, minutes, or seconds).

Finally, the function creates a timedelta object from the time_params dictionary and returns it.

There are several advantages to using this approach:

1. Flexibility: The function can handle time strings in a variety of formats, making it more useful in different situations.
2. Robustness: The function includes error checking to ensure that the input string is a valid time string. If it is not, the function raises a custom exception to indicate this.
3. Readability: The use of regular expressions and named groups makes the code more readable and easier to understand.
4. Efficiency: By using a dictionary to store the time components and a timedelta object to represent the final result, the function can handle the time calculations more efficiently.

Answer 12

Consider trying tempora.parse_timedelta (from tempora).

$ pip-run 'tempora>=4.1.1' -- -q
>>> from tempora import parse_timedelta
>>> parse_timedelta("32m")
datetime.timedelta(seconds=1920)
>>> parse_timedelta("2h32m")
datetime.timedelta(seconds=9120)
>>> parse_timedelta("4:13")
datetime.timedelta(seconds=15180)
>>> parse_timedelta("5hr34m56s")
datetime.timedelta(seconds=20096)