Re: [Tutor] please help
On 22Mar2014 00:04, Mark Lawrence wrote: > On 21/03/2014 21:39, Cameron Simpson wrote: > >On 21Mar2014 20:31, Mustafa Musameh wrote: > > > >I would collect the statistics using a dictionary to keep count of > >the characters. See the dict.setdefault method; it should be helpful. > > > > Delightfully old fashioned but I'd now prefer > http://docs.python.org/3/library/collections.html#collections.Counter > :) Maybe, but using a dictionary is easy and Mustafa will learn more. Cheers, -- Cameron Simpson Do not underestimate your abilities. That is your boss's job. It is your job to find ways around your boss's roadblocks. - Glen Appleby http://www.armory.com/~glena/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] (no subject)
On 03/21/2014 09:57 PM, Jerry Hill wrote: On Fri, Mar 21, 2014 at 3:25 PM, Gary Engstrom wrote: I am trying to understand function fibc code line a,b = b, a + b and would like to see it written line by line without combining multiply assignment. If possible. I sort of follow the right to left evaluation of the other code. Sure. a,b = b, a+b is equivalent to: new_a = b new_b = a + b a = new_a b = new_b del new_a del new_b That is, we first evaluate everything on the right hand side of the equals sign, then assign those values to a and b. Then we get rid of the temporary variables, since the original statement didn't leave any temporary variable floating around. In other words, it is like a = b ; b = a+b performed *in parallel*. Another way to write it is: old_a = a a = b b = old_a + b d ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Understanding code line
On 03/21/2014 06:14 PM, Gary wrote: Pythonists I am trying to understand the difference between a = b b = a + b and a,b = b, a+ b When used in my Fibonacci code the former generates 0,1,2,4,8,16,32 and the later Generates 0,1,1,2,3,5,8,13,21,34,55,89. The second is the sequence I want, but I would Like to understand the second code sequence better so I can write the code in R and Scilab as well as python. To understand a, b = b, a+ b correctly, think of it operating in parallel, each assignment independantly. So, it does what you think (and need to compute a fibonacci sequence). A better explanation, maybe, is that python has *tuples*, which are groups of values held together; and are better written inside parens (), like (1,2,3) or (x,y,z). But () are not compulsary, a comma is enough to make a tuple. Here we have two 2-tuples, also called pairs, meaning tuples of 2 values. The assignment thus actually means: (a, b) = (b, a+b) So, python *first* constructs the right side tuple, *then* assigns it to the left side; however, since we don't have on the left side a (named) tuple variable, it actually assigns to the local variables a & b, in //. Hope it's clear. You can consider this last step as nice, little magic. Rarely needed, but very handy when needed. d ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Fib sequence code assignment
On 03/21/2014 10:21 PM, Gary wrote: Dear Jerry, Thank you so much, once you see it it seems so clear, but to see it I might as well be in the Indian Ocean. Got kinda close using temporary variable,but didn't know enough to use del. A lesson learn. You don't need del (here). Every variable is automagically recycled at the end of the current scope, meaning usually the end of the function (fib). In practice, we so-to-say never need del in python (the common exception being to delete an item in a collection). d ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] please help
On 03/21/2014 10:39 PM, Cameron Simpson wrote: On 21Mar2014 20:31, Mustafa Musameh wrote: Please help. I have been search the internet to understand how to write a simple program/script with python, and I did not do anything. I have a file that look like this ID 1 agtcgtacgt… ID 2 acccttcc . . . in other words, it contains several IDs each one has a sequence of 'acgt' letters I need to write a script in python where the output will be, for example, like this ID 1 a = 10%, c = 40%, g=40%, t = 10% ID 2 a = 15%, c = 35%, g=35%, t = 15% . . . (i mean the first line is the ID and the second line is the frequency of each letter ) How I can tell python to print the first line as it is and count characters starting from the second line till the beginning of the next '>' and so on You want a loop that reads lines in pairs. Example: while True: line1 = fp.readline() print line1, line2 = fp.readline() ... process the line and report ... Then to process the line, iterate over the line. Because a line is string, and a string is a sequence of characters, you can write: for c in line2: ... collect statistics about c ... ... print report ... I would collect the statistics using a dictionary to keep count of the characters. See the dict.setdefault method; it should be helpful. I think it would be easier to do that in 2 loops: * first read the file line by line, building a list of pairs (id, base-sequence) (and on the fly check the input is correct, if needed) * then traverse the sequences of bases to get numbers & percentages, and write out d ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
