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bin/moonphase.py

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Python
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#!/usr/bin/env python3
"""
moonphase.py - Calculate Lunar Phase
Author: Sean B. Palmer, inamidst.com
Enhanced for Samizdat & Observatoř Cybernetics
Cf. http://en.wikipedia.org/wiki/Lunar_phase#Lunar_phase_calculation
"""
import math, decimal, datetime, sys
dec = decimal.Decimal
def position(now=None):
if now is None:
now = datetime.datetime.now()
diff = now - datetime.datetime(2001, 1, 1)
days = dec(diff.days) + (dec(diff.seconds) / dec(86400))
lunations = dec("0.20439731") + (days * dec("0.03386319269"))
return lunations % dec(1)
def phase(pos):
index = (pos * dec(8)) + dec("0.5")
index = math.floor(index)
return {
0: "New Moon",
1: "Waxing Crescent",
2: "First Quarter",
3: "Waxing Gibbous",
4: "Full Moon",
5: "Waning Gibbous",
6: "Last Quarter",
7: "Waning Crescent"
}[int(index) & 7]
def phase_cz(pos):
index = (pos * dec(8)) + dec("0.5")
index = math.floor(index)
return {
0: "Nov (New Moon)",
1: "Dorůstající srpek (Waxing Crescent)",
2: "První čtvrť (First Quarter)",
3: "Dorůstající Měsíc (Waxing Gibbous)",
4: "Úplněk (Full Moon)",
5: "Ubývající Měsíc (Waning Gibbous)",
6: "Poslední čtvrť (Last Quarter)",
7: "Ubývající srpek (Waning Crescent)"
}[int(index) & 7]
def illumination(pos):
# Approximate illumination percentage
# pos is 0 at New Moon, 0.5 at Full Moon, 1.0 at New Moon
p = float(pos)
return round((1 - math.cos(p * 2 * math.pi)) / 2 * 100, 1)
def moon_ascii(pos):
index = int((pos * dec(8)) + dec("0.5")) & 7
icons = ["🌑", "🌒", "🌓", "🌔", "🌕", "🌖", "🌗", "🌘"]
return icons[index]
def get_moon_metrics(now=None):
if now is None:
now = datetime.datetime.now()
pos = position(now)
p_name = phase(pos)
p_name_cz = phase_cz(pos)
illum = illumination(pos)
icon = moon_ascii(pos)
lunation_num = int(math.floor(float((now - datetime.datetime(2001, 1, 1)).days) / 29.53058867)) + 300 # relative count
roundedpos = round(float(pos), 4)
return {
"datetime": now.isoformat(),
"position": roundedpos,
"phase_en": p_name,
"phase_cz": p_name_cz,
"illumination_pct": illum,
"icon": icon,
"lunation_est": lunation_num,
"summary": f"{icon} {p_name_cz} | Phase: {roundedpos} | Illumination: {illum}%"
}
def main():
now = datetime.datetime.now()
m = get_moon_metrics(now)
if len(sys.argv) > 1 and sys.argv[1] == "--json":
import json
print(json.dumps(m, indent=2))
elif len(sys.argv) > 1 and sys.argv[1] == "--raw":
print(m["position"])
else:
print(m["summary"])
if __name__=="__main__":
main()