[newbie] troubles with tuples
I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? thanks in advance and kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] troubles with tuples
On Mon, Feb 3, 2014 at 11:50 AM, Jean Dupont jeandupont...@gmail.com wrote: I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? thanks in advance and kind regards, Some examples: a[start:end] # items start through end-1 a[start:] # items start through the rest of the array a[:end]# items from the beginning through end-1 a[:] # a copy of the whole array a[-1] # last item in the array a[-2:] # last two items in the array a[:-2] # everything except the last two items HTH, -larry -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] troubles with tuples
On Monday, February 3, 2014 6:50:31 PM UTC+2, Jean Dupont wrote: I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? thanks in advance and kind regards, jean Hi from http://docs.python.org/3.3/library/stdtypes.html?highlight=tuple#tuple The slice of s from i to j is defined as the sequence of items with index k such that i = k j. If i or j is greater than len(s), use len(s). If i is omitted or None, use 0. If j is omitted or None, use len(s). If i is greater than or equal to j, the slice is empty. so in above k j but not equal so in your example slice will be of only one member. /Asaf -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] troubles with tuples
On Monday, February 3, 2014 10:20:31 PM UTC+5:30, Jean Dupont wrote: I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) Python 2.7.6 (default, Jan 11 2014, 17:06:02) [GCC 4.8.2] on linux2 Type help, copyright, credits or license for more information. tup2=(1,2,3,4,5,6,7) tup2[0:1] (1,) So assuming you meant (1,) and wrote (2,) :-) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? Generally ranges in python are lower-inclusive upper-exclusive What some math texts write as [lo, hi) So if you want from index 1 to 2-inclusive it is 1 to 3 exclusive tup2[0:2] See for motivations http://www.cs.utexas.edu/~EWD/transcriptions/EWD08xx/EWD831.html And one more surprising thing to note is that negatives count from the end -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] troubles with tuples
Op maandag 3 februari 2014 18:06:46 UTC+1 schreef Rustom Mody: On Monday, February 3, 2014 10:20:31 PM UTC+5:30, Jean Dupont wrote: I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) Python 2.7.6 (default, Jan 11 2014, 17:06:02) [GCC 4.8.2] on linux2 Type help, copyright, credits or license for more information. tup2=(1,2,3,4,5,6,7) tup2[0:1] (1,) So assuming you meant (1,) and wrote (2,) :-) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? Generally ranges in python are lower-inclusive upper-exclusive What some math texts write as [lo, hi) So if you want from index 1 to 2-inclusive it is 1 to 3 exclusive tup2[0:2] See for motivations http://www.cs.utexas.edu/~EWD/transcriptions/EWD08xx/EWD831.html And one more surprising thing to note is that negatives count from the end Thank you (and the others) for making this logical kind regards, jean -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] troubles with tuples
On 2/3/2014 11:50 AM, Jean Dupont wrote: I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? thanks in advance and kind regards, This should be covered in the tutorial, which you should read if you have not already. -- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
Re: [newbie] troubles with tuples
On Mon, 03 Feb 2014 08:50:31 -0800, Jean Dupont wrote: I'm looking at the way to address tuples e.g. tup2 = (1, 2, 3, 4, 5, 6, 7 ); As I found out indices start with 0 in Python, so tup2[0] gives me 1, the first element in the tuple as expected tup2[1] gives me 2, the second element in the tuple as expected now here comes what surprises me: tup2[0:1] does not give me the expected (1,2) but (2,) what is the reason for this and how then should one get the first and the second element of a tuple? Or the 3rd until the 5th? thanks in advance and kind regards, jean tup = (0,1,2,3,4,5,6,7) tup[0:1] (0,) tup[1:2] (1,) tup[2:3] (2,) tup[0:2] (0, 1) tup[2:5] (2, 3, 4) This is as I'd expect, as the notation [0:1] means: starting from the 0th element, up to and including the element preceding the first element Or [m:n] means starting from the mth element, everything up to and including the element preceding the nth element Are you sure you got (2,) for [0:1] and not for [2:3]? Are you sure your initial tuple is what you thought it was? -- Denis McMahon, denismfmcma...@gmail.com -- https://mail.python.org/mailman/listinfo/python-list
