Re: [Tutor] adding columns of numbers
Christopher Spears wrote: > I've been reading an old copy of "Programming Python" > and started to work on one of its challenges. I have > a text file called table.txt: > > 1 5 10 2 1.0 > 2 10 20 4 2.0 3 > 3 15 30 8 3 2 1 > 4 20 40 16 4.0 > > I want to add each column of numbers, so the end > result would be a list like so: > > [10, 50, 100, 30 , 10.0, 5, 1] > > So far, I've been able to modify some code I found in > the book: > > #!/usr/bin/python > import string > > def summer(fileName): > for lines_in_file in open(fileName, 'r').readlines(): > cols_in_file = string.split(lines_in_file) > #print cols_in_file > numCols = len(cols_in_file) > sums = [0] * numCols This creates a new sums list for each line of the file. You need to initialize sums outside the loop. It's a little tricky to figure out how long sums really needs to be, since the lines are not all the same length. > #print sums > cols = string.split(lines_in_file) > #print cols > for i in range(numCols): > sums[i] = sums[i] + eval(cols[i]) Instead of eval(cols[i]) it would be better to use float(cols[i]). It's usually a good idea to avoid eval(). Extra credit: Write summer() as a one-liner. :-) (I know, I shouldn't be encouraging this. But it is a good exercise even if you wouldn't use it in production code. It would be pretty easy if the lines were all the same length...) Kent > return sums > > if __name__ == '__main__': > import sys > print summer(sys.argv[1]) > > Unfortunately, the output is: > [4, 20, 40, 16, 4.0] > > The code can read the file, but the code doesn't sum > the numbers to produce a new list. Any hints? > > > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] adding columns of numbers
On 02/02/07, Christopher Spears <[EMAIL PROTECTED]> wrote: > I've been reading an old copy of "Programming Python" > and started to work on one of its challenges. I have > a text file called table.txt: > > 1 5 10 2 1.0 > 2 10 20 4 2.0 3 > 3 15 30 8 3 2 1 > 4 20 40 16 4.0 > > I want to add each column of numbers, so the end > result would be a list like so: > > [10, 50, 100, 30 , 10.0, 5, 1] > > So far, I've been able to modify some code I found in > the book: > > #!/usr/bin/python > import string > > def summer(fileName): > for lines_in_file in open(fileName, 'r').readlines(): > cols_in_file = string.split(lines_in_file) > #print cols_in_file > numCols = len(cols_in_file) > sums = [0] * numCols > #print sums > cols = string.split(lines_in_file) > #print cols > for i in range(numCols): > sums[i] = sums[i] + eval(cols[i]) > return sums > > if __name__ == '__main__': > import sys > print summer(sys.argv[1]) > > Unfortunately, the output is: > [4, 20, 40, 16, 4.0] Compare the output with the input. Where do you think the output came from? Can you see how this is reflected in your code? -- John. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] adding columns of numbers
I've been reading an old copy of "Programming Python" and started to work on one of its challenges. I have a text file called table.txt: 1 5 10 2 1.0 2 10 20 4 2.0 3 3 15 30 8 3 2 1 4 20 40 16 4.0 I want to add each column of numbers, so the end result would be a list like so: [10, 50, 100, 30 , 10.0, 5, 1] So far, I've been able to modify some code I found in the book: #!/usr/bin/python import string def summer(fileName): for lines_in_file in open(fileName, 'r').readlines(): cols_in_file = string.split(lines_in_file) #print cols_in_file numCols = len(cols_in_file) sums = [0] * numCols #print sums cols = string.split(lines_in_file) #print cols for i in range(numCols): sums[i] = sums[i] + eval(cols[i]) return sums if __name__ == '__main__': import sys print summer(sys.argv[1]) Unfortunately, the output is: [4, 20, 40, 16, 4.0] The code can read the file, but the code doesn't sum the numbers to produce a new list. Any hints? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
