[Tutor] Re: Question on Regular Expression Help

[Alfred Milgrom]

 >> I have spent some time without success, trying to read a line of data 
containing four numbers and storing each number into a variable. The line 
that is read is the following, which has been shortened some to remove 
extra spaces for this example. MX/MN 91 72 90 70 These numbers represent 
temperatures, and can vary, such as -11, -1, 0, 9 23, 75, 102, etc. So in 
order to use a regular expression to search for the numbers, I have to 
check for a dash (-) with up to 2 digits after the dash, and whether their 
could be up to 3 digits in each number. The problem is that my code cannot 
extract these numbers to store into the variables t1, t2, t3, and t4.

Hi Henry:

I don't think it is necessary to use "re", as simple string operations and 
list comprehension do the job easily.

The following code illustrates the ideas:

def isnumber(str):
     digits = '-0123456789'
     for letter in str:
	if letter not in digits:
             return 0
     return 1

string = "MX/MN          91          72          90          70         "
list = string.split(' ')
list = [item for item in list if item and isnumber(item)]
if len(list) == 4:
     t1, t2, t3, t4 = list
     print t1, t2, t3, t4
else:
     print "line does not contain four numbers'

Hope this helps,
Fred Milgrom