this is my code, my array list holds 3 array, the problem is the output:
#🔒 array list
golden olive
elder scarabBOT
this is my code, my array list holds 3 array, the problem is the output:
@golden olive
Python help channel opened
golden olive
import array as a
import random as r
array1 = a.array("i", [])
array2 = a.array("i", [])
array3 = a.array("i", [])
for i in range(10):
array1.append(r.randint(1,10))
array2.append(r.randint(1,10))
array3.append(r.randint(1,10))
matrice = [[array1], [array2], [array3]]
print(matrice)
the output is "[[array('i', [3, 9, 5, 8, 8, 6, 1, 3, 2, 7])], [array('i', [10, 7, 1, 3, 5, 6, 9, 2, 1, 8])], [array('i', [4, 1, 5, 5, 4, 3, 9, 4, 10, 4])]]"
what i want is to remove every time the "[array('i',[])]" part
what can i do? i also can print the whole array list with a for loop, but i was searching for a better solution
what i tryed: strip, it dosent work
glad sigil
It's a weird way to create a 2d (?) matrix to begin with, but that is simply how an array is printed
You can make a function for printing it, but a better option is to use numpy
Are you allowed to use numpy? @golden olive
!e
import numpy as np
matrice = np.random.randint(1, 10, (3, 1))
print(matrice)
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
001 | [[7]
002 | [7]
003 | [3]]
No :(
golden olive
Also I wasn't at school when they started talking about array list, I can give you the code that they made but I don't understand it at all
There are no comments
glad sigil
sure
golden olive
from random import *
import array
r = int(input("inserisca il numero delle righe che vuole inserire "))
while r < 1 :
r = int(input("inserisca il numero delle righe che vuole inserire "))
c = int(input("inserisca il numero di colonne che vuole inserire "))
while c < 1 :
c = int(input("inserisca il numero delle colonna che vuole inserire "))
min = int(input("inserisca il valore minimo "))
max = int(input("inserisca il valore massimo "))
while max <= min :
max = int(input("inserisca il valore massimo "))
m = []
for y in range(r) :
ar1 = []
for i in range (c):
x = randint(min, max)
ar1.append(x)
m.append(ar1)
for j in range(r) :
for t in range (c) :
print(m[j][t], end="\t")
print()
for j in range (r):
max = min-1
for i in range(c) :
val1 = m[j][i]
if val1 > max :
max = val1
print (max)
That is the code they gave you?
golden olive
Yes
golden olive
I am working on a list of array, (someting like "list = [[list1],[list2],[list3]]
glad sigil
They are not using arrays though, but lists
golden olive
They are not using arrays though, but lists
i saw, but they used "import array"
the task is:
glad sigil
Their import array is pointless
golden olive
"create an array made of list, ask the user for the number of column and row and print the array"
its ramndom generated so also ask for min and max for the randint range
glad sigil
Is that translated, or the literal assignment text?
golden olive
this is the result of 5-5 with 1 as min and 10 as max
golden olive
Is that translated, or the literal assignment text?
thats what the code should do, the assignment was not given
glad sigil
Okay, and that code you just send was their solution to this assignment?
And you want to try and do it yourself now
golden olive
they just send the code saing "this is the code that we made"
golden olive
And you want to try and do it yourself now
also yes
glad sigil
The code they sent is not great to say it nicely... many beginner mistakes like shadowing existing function names, using 1 letter variable names, importing an entire module with *, importing a module and not using etc.
Take it with a grain of salt
And I think we can just use a list of lists
So not necessary to use array (if they do not use it either)
golden olive
And I think we can just use a list of lists
ok
tbh i dont understand that well how does list of list works
glad sigil
A list is just something that has a reference to one or multiple objects
So it can hold all types of different stuff
!e
my_list = [1, 2, "a", "abcdef", 5.0, None]
print(my_list)
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
[1, 2, 'a', 'abcdef', 5.0, None]
So this is an example of a list holding a few different objects
Like numbers, strings, etc.
This makes sense?
glad sigil
So when we create the list, we have the following:
A variable called "my_list" which refers to all kinds of objects
And we access each separate object by supplying an index, like my_list[0] refers to the object 1
And my_list[3] refers to "abcdef"
This makes sense?
golden olive
yeah
glad sigil
Okay, so a more complicated example now
!e
my_list = [0, [1, 2, 3], 4, 5, [6, 7], 8]
print(my_list)
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
[0, [1, 2, 3], 4, 5, [6, 7], 8]
golden olive
something like
for i in range(len(my_list)):
print(my_list[i], end=" ")
should print it all right?
golden olive
!e
```py
my_list = [0, [1, 2, 3], 4, 5, [6, 7], 8]
print(my_list)
```
ok so in a big list we added another list
how can we call them this time?
glad sigil
Yeah, so my_list refers to the "outer list"
And in this outer list we have some numbers, and some inner lists
So let's say we want to access the 8, we can value = my_list[5]
Does that make sense?
golden olive
So let's say we want to access the 7, how do we do that?
good question
golden olive
Maybe an easier question, how do we acess the `[6, 7]` list?
something like mylist[4][0]?
glad sigil
Is the [6, 7] at position 1 or 4 of my_list ?
golden olive
4
glad sigil
So we acess the item at index 4
!e
my_list = [0, [1, 2, 3], 4, 5, [6, 7], 8]
print(my_list[4])
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
[6, 7]
Okay, so now we have a reference to this inner list, we want acess to the 7
my_list = [0, [1, 2, 3], 4, 5, [6, 7], 8]
inner_list = my_list[4]
How do we get this value?
glad sigil
Right
golden olive
something like inner_list[1]
glad sigil
!e
my_list = [0, [1, 2, 3], 4, 5, [6, 7], 8]
inner_list = my_list[4]
value = inner_list[1]
print(value)
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
7
Exactly
And since inner_list is the same as my_list[4], we can shorten the two lines to value = my_list[4][1]
Is the same as inner_list[1]
Does this make sense?
golden olive
yeah
golden olive
my_list = [0, [1, 2, 3], 4, 5, [6, 7], 8]
value = my_list[1][2]
print(value)
Okay, think we got it so far
golden olive
why cant we just combine it in the print?
glad sigil
We can
I just want to show it in steps, so you understand why we can do my_list[a][b]
glad sigil
It's not a special syntax to do [a][b] on a list, it's just indexing an inner list, and then indexing from this inner list
So now we want to make a "2D matrix" with lists
So the idea would be that the outer list would hold a number of rows, and each row would hold a number of values/numbers
glad sigil
More like a rectangle
This would be the structure
An outer list with references to some other lists
Each list representing a row of the matrix
golden olive
can we make the first list (index 0) with a len of 4?
or everything need to be the same
glad sigil
We can actually do this, yes
But if we want to think of this outer list as a matrix, this would not make sense
Remember that the outer list can hold a reference to different types of objects
So the item at position 0 can even be a string or single number
Does not even need to be a list
golden olive
oh ok, i am understainding
glad sigil
So we could start with make the general structure
Which is a list holding a reference to a number of lists
Let's say we know the number of rows and columns
!e
rows = 4
columns = 3
matrix = []
...
@glad sigil :warning: Your 3.12 eval job has completed with return code 0.
[No output]
So now we want this outer list to hold a reference to how many lists?
golden olive
4
glad sigil
RIght, because each inner list holds item for a single row of the matrix
Are you able to add 4 empty lists to the matrix?
golden olive
no i dont think i can
glad sigil
Do you know how to make an empty list?
golden olive
like this []
glad sigil
Right
golden olive
but then i dont respect the 3 of colomns
glad sigil
We don't care about how many columns
We are just adding an empty list 4 times
We can fill these rows later on (3 values per row)
golden olive
We can fill these rows later on (3 values per row)
okk
with .append or .insert right?
glad sigil
Jup
and the same way we can add empty lists to the matrix
What do we use if we want to do the same thing multiple times?
golden olive
control c and control v?
glad sigil
We use a loop to repeat some code multiple times
We want to repeat this code 4 times (we add a row 4 times), so how do we write this with a loop
golden olive
yeah, but if we want to make the list all the same dont we use avariable?
glad sigil
A variable is just a reference to some value
Like a pointer to some value, or simply just a name you give some value
Okay, so repeating code 4 times, how do you do that?
golden olive
variable = [1,2,3]
my_list = [variable, variable, variable]
isnt this what we want to make?
glad sigil
There are some issues with that approach
First of all, you "hardcode" such that it adds 3 rows
We can have any number of rows
Second of all:
Do you see the issue here?
golden olive
yeah, every index of the list refer to the same
golden olive
so a for i in range(3) loop is the best
glad sigil
Okay
But we are given rows = ... and columns = ...
rows = 4
columns = 3
matrix = []
yes, let me try
golden olive
Actually, no
ok sorry i cant
glad sigil
Can you simply just write a loop that adds an empty list the correct number of times
golden olive
oh empty
glad sigil
Yes, no nested loop necessary, just a single for loop
golden olive
for i in range(row):
matrix.append([])
glad sigil
!e
rows = 4
columns = 3
matrix = []
for i in range(rows):
matrix.append([])
print(matrix)
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
[[], [], [], []]
rows not row but yes correct
golden olive
sorry
glad sigil
So now we have the general structure
Now let's say we want to add columns items to the first row of the matrix
How do we access the first row? row = ...
golden olive
matrix[0]
golden olive
a for loop
glad sigil
And let's say we want to add a random integer that number of times
And we have a minimum and maximum value for this random integer
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
for i in range(rows):
matrix.append([])
row = matrix[0]
for ...:
...
Can you fill in the dots to add the correct number of random values to the first row?
glad sigil
Yes, so let's import random indeed
And use random.randint(...)
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
for i in range(rows):
matrix.append([])
row = matrix[0]
for i in range(columns):
random_value = random.randint(min_value, max_value)
Fill in the dots
golden olive
min, max
glad sigil
again?
glad sigil
```py
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix ...
We defined the minimum and maximum in this code
What values do we use
glad sigil
Okmay so filled in the dots
And then we want to add it to the first row, so what do we add to the for loop?
glad sigil
Give the entire line of code we should add
glad sigil
!e
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
for i in range(rows):
matrix.append([])
row = matrix[0]
for i in range(columns):
random_value = random.randint(min_value, max_value)
row.append(random_value)
print(matrix)
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
[[1, 7, 1], [], [], []]
Right, and because we have 4 separate lists (and not 4 reference to a single list) we get this output
So we have succesfully filled in one of the rows
But obviously we want to do this for every row
golden olive
i have an idea
let me write it one sec
for i in range(row):
row = matrix[i]
for j in range(columns):
random_value = random.randint(min_value, max_value)
row.append(random_value)
!e
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
for i in range(rows):
matrix.append([])
for i in range(rows):
row = matrix[i]
for j in range(columns):
random_value = random.randint(min_value, max_value)
row.append(random_value)
print(matrix)
we fill the first with index 0, the the for continues with an i = 1
elder scarabBOT
@glad sigil :white_check_mark: Your 3.12 eval job has completed with return code 0.
[[7, 10, 5], [9, 4, 3], [4, 10, 2], [2, 1, 2]]
sorry i forgot the s
golden olive
lez go!
glad sigil
So the only thing to change is that you should ask the user for the rows, columns and min_value and max_value
golden olive
so now my matrix its a list of list were everything is created randomly
glad sigil
Jup
golden olive
this is even better than the code that my class made
only ptoblem is to make a good print as they made
glad sigil
So it should be printed for each row with tabs then?
golden olive
Yeah
But that doesn't seem to hard
We take 1 rows at the time and print it index by index
And use an ,end="/t" for the tab space
Right?
glad sigil
They also seem to print the maximum* value for each row
for j in range (r):
max = min-1
for i in range(c) :
val1 = m[j][i]
if val1 > max :
max = val1
print (max)
This part
Prints the maximum value of each row
And before that they print each value with a tab after it
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
# Create an empty matrix
for i in range(rows):
matrix.append([])
# Fill the matrix
for i in range(rows):
row = matrix[i]
for j in range(columns):
row.append(random.randint(min_value, max_value))
print(matrix)
So this is our code so far
Simplified the filling in to one line
Can you create some code for printing?
golden olive
Let me try
!e
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
# Create an empty matrix
for i in range(rows):
matrix.append([])
# Fill the matrix
for i in range(rows):
row = matrix[i]
for j in range(columns):
row.append(random.randint(min_value, max_value))
for i in range(rows):
row = matrix[i]
for j in row:
print(j, end="\t")
print() # New line for the new row
print(f"\nmin: {min_value}\nmax: {max_value}") # For max and min, \n just to space
@golden olive :white_check_mark: Your 3.12 eval job has completed with return code 0.
001 | 7 1 5
002 | 6 10 9
003 | 9 10 4
004 | 4 10 6
Jup, that is what they had as well
You can see it still screws up the allignment a bit
There are ways to fix this, but they are probably a bit too advanced for now
glad sigil
Well not really, they want to print the minimum value for each row of the matrix
glad sigil
Which is random each time (because the matrix is randomly filled)
golden olive
cant we just use the min() function?
glad sigil
Yeah haha, but they shadow over it by doing min = ...
So now min holds a value instead of the function that gives you a minimum value
We could still do that because we don't replace the value of min since we named our variable min_value
So in that case we can do
for row in matrix:
print(min(row))
But they might want you to do it without the min function
golden olive
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
# Create an empty matrix
for i in range(rows):
matrix.append([])
# Fill the matrix
for i in range(rows):
row = matrix[i]
for j in range(columns):
row.append(random.randint(min_value, max_value))
for i in range(rows):
row = matrix[i]
for j in row:
print(j, end="\t")
print("\tmin:",min(row))
print() # New line for the new row
ok let me try
glad sigil
I would do it separately
Not in the other loop (they would print interleaved that way)
golden olive
okk
the teacher like to make the code more hard than it should be
let me see if i can make withoiut the function
glad sigil
Yeah, I would really try to find your resources elsewhere, this teacher is not proficient with Python at all
This is code that someone with a few weeks (maybe a month or two) of experience would make
golden olive
!e
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
# Create an empty matrix
for i in range(rows):
matrix.append([])
# Fill the matrix
for i in range(rows):
row = matrix[i]
for j in range(columns):
row.append(random.randint(min_value, max_value))
for i in range(rows):
row = matrix[i]
for j in row:
print(j, end="\t")
print() # New line for the new row
for i in range(rows):
min = max_value # Biggest value possible in the code, reset the variable
row = matrix[i]
for j in row:
if j < min:
min = j
print("min value for row",i,"is:",min)
@golden olive :white_check_mark: Your 3.12 eval job has completed with return code 0.
001 | 6 9 1
002 | 3 1 3
003 | 8 6 3
004 | 2 5 10
005 | min value for row 0 is: 1
006 | min value for row 1 is: 1
007 | min value for row 2 is: 3
008 | min value for row 3 is: 2
emh
glad sigil
Do you see that min and max is highlighted?
golden olive
we started school in september, started python in that moment
golden olive
Do you see that `min` and `max` is highlighted?
yesh because they are function
golden olive
idk why in vs code i dont get the color
glad sigil
Otherwise we could not use the min and max function after that
You'll remember most of the names after some practice
vscode syntax highlighter is just not that smart I guess
golden olive
yeaht thats a good idea
and put a lot of comment
the code without them is not readable
glad sigil
Same goes for the for i in range(rows) and for j in range(columns), might as well do for row_nr in range(rows) f.e.
If your variable names make sense, then comments are not as necessary
glad sigil
It's kind of subjective. Doing from random import randint makes it so you only have to write randint(0, 10) in your code instead of random.randint(0, 10) f.e
This is shorter, but it is unclear where this function randint comes from in your code
So when someone reads your code and sees randint they will need to search up what kind of function this is
But if you do random.randint(0, 10) it is already clear where the function comes from
golden olive
oh ok, well yeah its less intuitive
glad sigil
Also, multiple modules can have a function randint
golden olive
and what does "from random import *" mean
golden olive
Also, multiple modules can have a function `randint`
code 💥
glad sigil
it basically means from random import randint, randrange, random, ....
So importing literally everything from the random module
golden olive
oh so the less intuitive thing to do
glad sigil
Without the need to write random. in the code
Yes, and you are filling the "namespace" with all the crap inside random
So it's a bad practice
golden olive
so the code of my class was litherally the wrost thing
glad sigil
Yeah it sucks pretty bad for a teacher
This would be my final code
import random
rows = 4
columns = 3
min_value = 1
max_value = 10
matrix = []
# Create an empty matrix
for i in range(rows):
matrix.append([])
# Fill the matrix
for row_nr in range(rows):
for j in range(columns):
matrix[row_nr].append(random.randint(min_value, max_value))
# Print the matrix
for row_nr in range(rows):
for value in matrix[row_nr]:
print(value, end="\t")
print() # New line for the new row
# Print the maximum value for each row
for row_nr in range(rows):
max_row_value = max_value # Biggest value possible in the code, reset the variable
for value in matrix[row_nr]:
if value > max_row_value:
max_row_value = value
print("max value for row", row_nr, "is:", max_row_value)
Shortened some things (like not doing row = ... but directly using matrix[row_nr])
golden olive
This would be my final code
```py
import random
rows = 4
columns = 3
min_value...
wait no
its the minimun value
glad sigil
In their code they want the maximum value iirc
golden olive
idk they did a lot of strange stuff
glad sigil
yeah like I said, many weird beginner mistakes, or at the very least mistakes by not knowing python very well
And the short variable names and stuff make it seem like they are just bad at making readable code in general
golden olive
tomorrow i will have python lesson, thx to you i will understand it
glad sigil
Yeah hope it helped, took a bit of time, but it should make it a bit more sense ;D
golden olive
And the short variable names and stuff make it seem like they are just bad at ma...
idk, i wasnt i class. maybe they did it for a reson
golden olive
Yeah hope it helped, took a bit of time, but it should make it a bit more sense ...
thx you so much for the help and for theaching me. now i can say that i know how to use matrix
bye, thx again
!solved
elder scarabBOT
Python help channel closed