Little implementation of http://janmatuschek.de/LatitudeLongitudeBoundingCoordinates code for get the bounding box coordinates of a geographical point.

gistfile1.py

degLat = -12.04930
degLon = -77.08223

radLat = math.radians(degLat)
radLon = math.radians(degLon)

MIN_LAT = math.radians(-90)	# -PI/2
MAX_LAT = math.radians(90)	#  PI/2
MIN_LON = math.radians(-180)	# -PI
MAX_LON = math.radians(180)	#  PI

distance = 0.5
radius = 6371.01

if radius < 0 and distance < 0:
    raise Exception(":o")

radDist = distance/radius

minLat = radLat - radDist
maxLat = radLat + radDist

minLon = 0
maxLon = 0

if minLat > MIN_LAT and maxLat < MAX_LAT :
	deltaLon = math.asin(math.sin(radDist) / math.cos(radLat))
	minLon = radLon - deltaLon
	if minLon < MIN_LON:
		minLon += 2 * math.pi 
	maxLon = radLon + deltaLon
	if maxLon > MAX_LON:
		maxLon -= 2 * math.pi
else:
        minLat = math.max(minLat, MIN_LAT)
	maxLat = math.min(maxLat, MAX_LAT)
	minLon = MIN_LON
	maxLon = MAX_LON

# RETURNS
"""
MIN LAT -12.053796601
MAX LAT -12.044803399
MIN LON -77.0868279003
MAX LON -77.0776320997
"""
# Show points in http://www.geoplaner.com/