Did you ever want to know how how many square inches are in a square meter? This short Python code allows you to get the answer. It uses a dictionary to simplify the conversions. Could be the start of a nice GUI program using radio buttons.

```
# convert area units, also has error trapping
# tested with Python24 vegaseat 01aug2005
#create an empty dictionary
areaD = {}
# populate dictionary using indexing and assignment with units and conversion factors relative to sqmeter = 1.0
# to convert x sqmeters to any of the other area units multiply by the factor
# to convert x of any of the other area units to sqmeter divide by the factor
# to convert x of any area unit to any of the other area units go over interim sqmeter
# this minimizes the total number of conversion factors
areaD['sqmeter'] = 1.0
areaD['sqmillimeter'] = 1000000.0
areaD['sqcentimeter'] = 10000.0
areaD['sqkilometer'] = 0.000001
areaD['hectare'] = 0.0001
areaD['sqinch'] = 1550.003
areaD['sqfoot'] = 10.76391
areaD['sqyard'] = 1.19599
areaD['acre'] = 0.0002471054
areaD['sqmile'] = 0.0000003861022
def convertArea(x, unit1, unit2):
"""area conversion with error trapping"""
if (unit1 in areaD) and (unit2 in areaD):
factor1 = areaD[unit1]
factor2 = areaD[unit2]
return factor2*x/factor1
else:
return False
# test1: x square-miles have how many acres?
x = 1.0
unit1 = 'sqmile'
unit2 = 'acre'
outcome = convertArea(x, unit1, unit2)
if outcome is not False:
print "1) %f %s = %f %s" % (x, unit1, outcome, unit2)
else:
print "1) There was an error converting %s to %" % (unit1, unit2)
# test2: force an error, misspelled unit is not in the dictionary
unit2 = 'acres'
outcome = convertArea(x, unit1, unit2)
if outcome is not False:
print "2) %f %s = %f %s" % (x, unit1, outcome, unit2)
else:
print "2) There was an error converting %s to %s" % (unit1, unit2)
```