def read_weather_data(r):

'''Read weather data from reader r in fixed-width format.

The field widths are:

4,2,2 YYYYMMDD (date)

2,2,2 DDMMSS (latitude)

2,2,2 DDMMSS (longitude)

6,6,6 FF.FFF (temp, deg. C; humidity, %; pressure, kPa)

The result is a list of tuples (not tuples of tuples),

where each tuple is of the form:

(YY, MM, DD, DD, MM, SS, DD, MM, SS, Temp, Hum, Press)'''

fields = ((4, int), (2, int), (2, int), # date

(2, int), (2, int), (2, int), # latitude

(2, int), (2, int), (2, int), # longitude

(6, float), (6, float), (6, float)) # data

result = []

# For each record

for line in r:

start = 0

record = []

# for each field in the record

for (width, target_type) in fields:

# convert the text

text = line[start:start+width]

field = target_type(text)

# add it to the record

record.append(field)

# move on

start += width

# add the completed record to the result

result.append(record)

return result