I have this list
list = [[0, 0], [0, 1], [0, 2], [1, 0], [1, 1], [1, 2], [2, 1], [2, 2], [2, 0]]
I want to take 2 integers
row = 2 and column = 1
Combine them
thing = (str(row) + str(", ") + str(column))
then I want to remove the list
[2, 1]
from the array. How would I do this?
EDIT: The language is Python
First of all, don't name your list list. It will overwrite the builtin function list() and potentially mess with your code later.
Secondly, finding and removing elements in a list is done like
data.remove(value)
or in your case
data.remove([2, 1])
Specifically, where you are looking for an entry [row, column], you would do
data.remove([row, column])
where row and column are your two variables.
It may be a bit confusing to name them row and column, though. because your data could be interpreted as a matrix/2D array, where "row" and "column" have a different meaning.
Related
hope doing well.
Is it possible to merge two big numpy array to make a several ones. These two arrays have the same number of rows. One array contains some names:
name_arr = [[sub_1],
[sub_2],
[sub_3],
...
[sub_n]]
The other one has some values:
value_arr = [[1, 2, 3],
[5, 2, -1],
[0, 0, 4],
...
[6, 18,200]]
Now, I want to extract numpy arrays using both the name_arr and value_arr. To be clear, I want to extract arrays with the names coming from name_arr and values coming from value_arr:
sub_1= [[1, 2, 3]]
sub_2= [[1, 2, 3]]
sub_3= [[0, 0, 4]]
...
sub_4= [[6, 18,200]]
I tried to use a for loop, but it was not successful:
for i in name_arr:
for j in value_arr:
if i == j:
name_arr [0, i] = value_arr [0, j]
but it was not successful at all ...
FYI, I made the arrays by splitting a dictionary,
Dict_data = {'sub_1' : [1, 2, 3],
'sub_2' : [5, 2, -1],
'sub_3' : [0, 0, 4],
... ,
'sub_n' : [6, 18,200]}
in case of having a solution to do my extraction directly from the dictionary, I deeply appreciate that. definitely I prefer to find a was to extract numpy arrays with the name of my keys and related data.
In advance, I appreciate any feedback.
Regards
I assume your name array contains strings as follows:
name_arr = ['sub_1',
'sub_2',
'sub_3',
...
'sub_n']
in this case you can simply do it with a for loop:
my_dict = {}
for i in range(len(name_arr)):
my_dict[name_arr[i]] = value_arr[i, :]
This is probably a very basic question but I dont know what I have to search for to find the answer for it:
I have this code:
list = [[0,1],[0,2],[1,3],[1,4],[1,5]]
list.append(list[0])
for i in list:
i.append(0)
print(list)
This List will later be used as coordinates for a curve. I need to duplicate the first coordinate at the end to get a closed curve.
If I then want to add a third value to each coordinate in the list the first and last item in list will be iterated over twice:
[[0, 1, 0, 0], [0, 2, 0], [1, 3, 0], [1, 4, 0], [1, 5, 0], [0, 1, 0, 0]]
I am guessing they have the same memory address and thereby the append-function is applied to the same object at this address once for the first index and once for the last.
What is this phenomenon called ? what is the easiest way to get the list like this:
[[0, 1, 0], [0, 2, 0], [1, 3, 0], [1, 4, 0], [1, 5, 0], [0, 1, 0]]
Thank you for your help
You can do a list comprehension:
list = [[0,1],[0,2],[1,3],[1,4],[1,5]]
list.append(list[0])
list = [x + [0] for x in list]
print(list)
# [[0, 1, 0], [0, 2, 0], [1, 3, 0], [1, 4, 0], [1, 5, 0], [0, 1, 0]]
EDIT: The trick here is, using x + [0] within the list comprehension. This way new lists are created, thus you do not append 0 to the same list twice (Hattip to #dx_over_dt)
The problem you have with your approach is, that the first and last element of your list refers to the very same object. You can see this, when you print i and list for every iteration:
for i in list:
i.append(0)
print(i)
print(list)
So for the first and last i in your loop, you will append a 0 to the very same list.
You could stick to your approach appending a copy of the first element:
list.append(list[0].copy())
The simplest answer is to add the 0's before appending the closing point.
list = [[0,1],[0,2],[1,3],[1,4],[1,5]]
for i in list:
i.append(0)
list.append(list[0])
print(list)
It's the tiniest bit more efficient than a list comprehension because it's not making copies of the elements.
I have to create a list of lists that is summarized below:
list_of_lists = [[0,1],[0,2],[0,3]....[0,N]]
Basically just need the first element of each sub-list to be 0, and the second element to be 1 more than the prior value of the second element.
The value for N is about 2000, so obviously I do not want to type out the whole thing. Is there a simple way to automate with Python?
Thank You
You can use simple list comprehension with range:
>>> N = 5
>>> [[0, i] for i in range(1, N + 1)]
[[0, 1], [0, 2], [0, 3], [0, 4], [0, 5]]
When I attempt iteration across columns in a row, the column does no change within a nested loop:
i_rows = 4
i_cols = 3
matrix = [[0 for c in xrange(i_cols)] for r in xrange(i_rows)]
for row, r in enumerate(matrix):
for col, c in enumerate(r):
r[c] = 1
print matrix
Observed output
[[1, 0, 0], [1, 0, 0], [1, 0, 0], [1, 0, 0]]
Expected output
[[1, 1, 1], [1, 1, 1], [1, 1, 1], [1, 1, 1]]
I have tried different expressions such as xrange() and len() and I am considering switching to numpy. I am a bit surprised that a two-dimensional array in Python is not so intuitive as my first impression of the language.
The goal is a two-dimensional array with varying integer values, which I later need to parse to represent 2D graphics on the screen.
How can I iterate across columns in a list of lists?
You just have to assign the value against the col, not c
for row, r in enumerate(matrix):
for col, c in enumerate(r):
r[col] = 1 # Note `col`, not `c`
Because the first value returned by enumerate will be the index and the second value will be the actual value itself.
I have a list[5][5] to populate... it looks like a table with 5 columns and 5 rows.
Each cell can be either one or zero.
I want to find different 2^25 possibility that can exist. Each possiblity is a combination of either 0 or 1 in a 5*5 table/list
How can I do that? With nested loop or something?
I suggest you start small... with a 1x1 list first and check that you can display both of the available combinations:
[[0]]
[[1]]
Next up, try a 2x2 list. There are 16 different lists to display:
[[0, 0], [0, 0]]
[[0, 0], [0, 1]]
[[0, 0], [1, 0]]
[[0, 0], [1, 1]]
[[0, 1], [0, 0]]
[[0, 1], [0, 1]]
[[0, 1], [1, 0]]
[[0, 1], [1, 1]]
[[1, 0], [0, 0]]
[[1, 0], [0, 1]]
[[1, 0], [1, 0]]
[[1, 0], [1, 1]]
[[1, 1], [0, 0]]
[[1, 1], [0, 1]]
[[1, 1], [1, 0]]
[[1, 1], [1, 1]]
If you've got the algorithm right for 1x1 and 2x2, then you should be able to generalise it to print your 5x5.
Good luck!
Update
Since you appear to be still struggling, here's a little extra help.
Break this problem into smaller problems. I'd start with generating the values. If you ignore the list notation in my examples above, you'll see that the sequence of values is one that is recognisable to every computer scientist on the planet. It's also pretty easy to generate in Python using bin() and str.zfill().
The second problem is putting them into lists. This isn't too hard either. Supposing the first value in your sequence is '0000'. You know that your lists are two rows by two columns. You can put the first two characters into a list and put that list into a list. Then put the next two characters into a list and append that list to the previous one. Done. Repeat for each value in the sequence.
Hope this helps.
You could try:
import itertools
gen = itertools.product((0,1),repeat=25)
To create a generator to get all of the combinations in 1d and then reshape the data as needed.