I have 1000 variables, a1,a2,a3,a4,a5 and so on. Is there a way to initialize all to value 100 using loop
My attempt:
for i in range(1,1001):
"a"i=100
I am missing basic syntax here.
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6Well why you need to declare 1000 variables ?Tanveer Alam– Tanveer Alam2015-05-02 05:43:18 +00:00Commented May 2, 2015 at 5:43
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Use an array or the Python equivalent...Ismael Miguel– Ismael Miguel2015-05-02 05:44:13 +00:00Commented May 2, 2015 at 5:44
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stackoverflow.com/questions/521674/… might be of use.bentank– bentank2015-05-02 05:48:33 +00:00Commented May 2, 2015 at 5:48
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@TanveerAlam..You can imagine a chess baord layout with each block having name as a1,a2..a8,b1.....h8. Now i dont want to write 64 different lines like a1=100,a2=100 etc. I want to do it by loop.Saurabh Shrivastava– Saurabh Shrivastava2015-05-02 05:55:18 +00:00Commented May 2, 2015 at 5:55
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2This question has so many duplicates that I couldn't find which one is the canonical version, if there even is one. See Why you don't want to dynamically create variables for links to 11 more dups.abarnert– abarnert2015-05-02 06:29:07 +00:00Commented May 2, 2015 at 6:29
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4 Answers
Don't ever ever do this. You gain absolutely nothing from doing it this way. How can you possibly REFER to these variables dynamically if you're setting them this way? Use a list or a dictionary instead.
a_list = [None] + [100] * 1000
# `a_list[n]` in place of `an`, here
a_dict = {num:100 for num in range(1, 1001)}
# `a_dict[n]` in place of `an`, here
edit for your chess board analogy:
import string
class ChessBoard(list):
def __init__(self, side_length, initial_value=None):
super().__init__()
for _ in range(side_length):
self.append([initial_value for _ in range(side_length)])
def get(self, notation):
"""Maps chess notation to the 2D list"""
indices = dict([(lett, num) for num,lett in
enumerate(string.ascii_letters, start=1)])
# {'a':1, 'b':2, ... 'Z':52}
x, y = indices[notation[0]]-1, int(notation[1])-1
return self[y][x]
board = ChessBoard(1000, 100) # how do we index the 1000th...nevermind
board.get("a6")
2 Comments
user2357112
Rather than sticking a
None at the start of the list, it's a better idea to just get used to 0-indexing. None-padding creates awkward issues like len being one higher than the number of logical elements of the list.
Adam Smith
@user2357112 agreed, which is why I implicitly converted from zero-indexing in the elegant solution. However if he's going to try and reference an element like you would a chess board, he needs to have 1-indexing.
I'll reiterate that this is a bad practice but you could do this.
for i in xrange(1, 1001):
globals()['a%s' % i] = 100
for i in xrange(1, 1001):
name = 'a%d' % i
print '%s = %d' % (name, globals()[name])
The second loop just prints them.
Comments
To do something like this you really ought to use a list. Initializing a length 1000 list with each entry set to 100 can be done by
a = [100] * 1000
You can set variables like this outside a list using exec, but that is not good practice unless you have some strange compelling reason to do so.
Note that the entries will be indexed from 0 to 999.
Comments
You can do this using Python Arrays/Lists. For your case you could create a list of 1000 100s by doing the following:
my_array = [100]*1001
To find a certain value in that list you "index" into it. For example:
print(my_array[300])
The print statement would print the 301st value in the list (as array indexes start counting at 0).
Comments
