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https://github.com/kylebarron/suncalc-py
A Python port of suncalc.js for calculating sun position and sunlight phases
https://github.com/kylebarron/suncalc-py
numpy sun sunrise sunset
Last synced: 7 days ago
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A Python port of suncalc.js for calculating sun position and sunlight phases
- Host: GitHub
- URL: https://github.com/kylebarron/suncalc-py
- Owner: kylebarron
- License: mit
- Created: 2020-11-19T23:27:02.000Z (about 4 years ago)
- Default Branch: master
- Last Pushed: 2024-04-15T13:38:53.000Z (9 months ago)
- Last Synced: 2024-12-23T07:28:31.838Z (17 days ago)
- Topics: numpy, sun, sunrise, sunset
- Language: Python
- Homepage:
- Size: 37.1 KB
- Stars: 61
- Watchers: 4
- Forks: 9
- Open Issues: 9
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
# suncalc-py
A fast, vectorized Python implementation of [`suncalc.js`][suncalc-js] for
calculating sun position and sunlight phases (times for sunrise, sunset, dusk,
etc.) for the given location and time.
[suncalc-js]: https://github.com/mourner/suncalc
While other similar libraries exist, I didn't originally encounter any that met
my requirements of being openly-licensed, vectorized, and simple to use 1.
## Install
```
pip install suncalc
```
## Using
### Example
`suncalc` is designed to work both with single values and with arrays of values.
First, import the module:
```py
from suncalc import get_position, get_times
from datetime import datetime
```
There are currently two methods: `get_position`, to get the sun azimuth and
altitude (in radians) for a given date and position, and `get_times`, to get sunlight phases
for a given date and position.
```py
date = datetime.now()
lon = 20
lat = 45
get_position(date, lon, lat)
# {'azimuth': -0.8619668996997687, 'altitude': 0.5586446727994595}
get_times(date, lon, lat)
# {'solar_noon': Timestamp('2020-11-20 08:47:08.410863770'),
# 'nadir': Timestamp('2020-11-19 20:47:08.410863770'),
# 'sunrise': Timestamp('2020-11-20 03:13:22.645455322'),
# 'sunset': Timestamp('2020-11-20 14:20:54.176272461'),
# 'sunrise_end': Timestamp('2020-11-20 03:15:48.318936035'),
# 'sunset_start': Timestamp('2020-11-20 14:18:28.502791748'),
# 'dawn': Timestamp('2020-11-20 02:50:00.045539551'),
# 'dusk': Timestamp('2020-11-20 14:44:16.776188232'),
# 'nautical_dawn': Timestamp('2020-11-20 02:23:10.019832520'),
# 'nautical_dusk': Timestamp('2020-11-20 15:11:06.801895264'),
# 'night_end': Timestamp('2020-11-20 01:56:36.144269287'),
# 'night': Timestamp('2020-11-20 15:37:40.677458252'),
# 'golden_hour_end': Timestamp('2020-11-20 03:44:46.795967773'),
# 'golden_hour': Timestamp('2020-11-20 13:49:30.025760010')}
```
These methods also work for _arrays_ of data, and since the implementation is
vectorized it's much faster than a for loop in Python.
```py
import pandas as pd
df = pd.DataFrame({
'date': [date] * 10,
'lon': [lon] * 10,
'lat': [lat] * 10
})
pd.DataFrame(get_position(df['date'], df['lon'], df['lat']))
# azimuth altitude
# 0 -1.485509 -1.048223
# 1 -1.485509 -1.048223
# ...
pd.DataFrame(get_times(df['date'], df['lon'], df['lat']))['solar_noon']
# 0 2020-11-20 08:47:08.410863872+00:00
# 1 2020-11-20 08:47:08.410863872+00:00
# ...
# Name: solar_noon, dtype: datetime64[ns, UTC]
```
If you want to join this data back to your `DataFrame`, you can use `pd.concat`:
```py
times = pd.DataFrame(get_times(df['date'], df['lon'], df['lat']))
pd.concat([df, times], axis=1)
```
### API
#### `get_position`
Calculate sun position (azimuth and altitude) for a given date and
latitude/longitude
- `date` (`datetime` or a pandas series of datetimes): date and time to find sun position of. **Datetime must be in UTC**.
- `lng` (`float` or numpy array of `float`): longitude to find sun position of
- `lat` (`float` or numpy array of `float`): latitude to find sun position of
Returns a `dict` with two keys: `azimuth` and `altitude`. If the input values
were singletons, the `dict`'s values will be floats. Otherwise they'll be numpy
arrays of floats.
#### `get_times`
- `date` (`datetime` or a pandas series of datetimes): date and time to find sunlight phases of. **Datetime must be in UTC**.
- `lng` (`float` or numpy array of `float`): longitude to find sunlight phases of
- `lat` (`float` or numpy array of `float`): latitude to find sunlight phases of
- `height` (`float` or numpy array of `float`, default `0`): observer height in meters
- `times` (`Iterable[Tuple[float, str, str]]`): an iterable defining the angle above the horizon and strings for custom sunlight phases. The default is:
```py
# (angle, morning name, evening name)
DEFAULT_TIMES = [
(-0.833, 'sunrise', 'sunset'),
(-0.3, 'sunrise_end', 'sunset_start'),
(-6, 'dawn', 'dusk'),
(-12, 'nautical_dawn', 'nautical_dusk'),
(-18, 'night_end', 'night'),
(6, 'golden_hour_end', 'golden_hour')
]
```
Returns a `dict` where the keys are `solar_noon`, `nadir`, plus any keys passed
in the `times` argument. If the input values were singletons, the `dict`'s
values will be of type `datetime.datetime` (or `pd.Timestamp` if you have pandas
installed, which is a subclass of and therefore compatible with
`datetime.datetime`). Otherwise they'll be pandas `DateTime` series. **The
returned times will be in UTC.**
## Benchmark
This benchmark is to show that the vectorized implementation is nearly 100x
faster than a for loop in Python.
First set up a `DataFrame` with random data. Here I create 100,000 rows.
```py
from suncalc import get_position, get_times
import pandas as pd
def random_dates(start, end, n=10):
"""Create an array of random dates"""
start_u = start.value//10**9
end_u = end.value//10**9
return pd.to_datetime(np.random.randint(start_u, end_u, n), unit='s')
start = pd.to_datetime('2015-01-01')
end = pd.to_datetime('2018-01-01')
dates = random_dates(start, end, n=100_000)
lons = np.random.uniform(low=-179, high=179, size=(100_000,))
lats = np.random.uniform(low=-89, high=89, size=(100_000,))
df = pd.DataFrame({'date': dates, 'lat': lats, 'lon': lons})
```
Then compute `SunCalc.get_position` two ways: the first using the vectorized
implementation and the second using `df.apply`, which is equivalent to a for
loop. The first is more than **100x faster** than the second.
```py
%timeit get_position(df['date'], df['lon'], df['lat'])
# 41.4 ms ± 437 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%timeit df.apply(lambda row: get_position(row['date'], row['lon'], row['lat']), axis=1)
# 4.89 s ± 184 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
```
Likewise, compute `SunCalc.get_times` the same two ways: first using the
vectorized implementation and the second using `df.apply`. The first is **2800x
faster** than the second! Some of the difference here is that under the hood the
non-vectorized approach uses `pd.to_datetime` while the vectorized
implementation uses `np.astype('datetime64[ns, UTC]')`. `pd.to_datetime` is
really slow!!
```py
%timeit get_times(df['date'], df['lon'], df['lat'])
# 55.3 ms ± 1.91 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
%time df.apply(lambda row: get_times(row['date'], row['lon'], row['lat']), axis=1)
# CPU times: user 2min 33s, sys: 288 ms, total: 2min 34s
# Wall time: 2min 34s
```
---
1: [`pyorbital`](https://github.com/pytroll/pyorbital) looks great but is
GPL3-licensed; [`pysolar`](https://github.com/pingswept/pysolar) is also
GPL3-licensed; [`pyEphem`](https://rhodesmill.org/pyephem/) is LGPL3-licensed.
[`suncalcPy`](https://github.com/Broham/suncalcPy) is another port of
`suncalc.js`, and is MIT-licensed, but doesn't use Numpy and thus isn't
vectorized. I recently discovered [`sunpy`](https://github.com/sunpy/sunpy) and
[`astropy`](https://github.com/astropy/astropy), both of which probably would've
worked but I didn't see them at first and they look quite complex for this
simple task...