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Reversing array without reverse function but loop isn't working

So I am trying to reverse an array from a .txt file without using the reverse function. here is what I have.
numbers = read() #creates numbers array out of the txt file
numbersrev = numbers #blank array for reverse
numLength = len(numbers) #measures the length of the array
print(numbers)
print("Array length of numbers: ", numLength)
i = numLength
i = i-1 #since the array starts at 0 instead of 1
k = 0
for k in range(8):
numbersrev[k] = numbers[i]
print ("The ", i," element of numbers is the ", k," element of numbersrev")
i -= 1
k += 1
print(numbersrev)
This is what I get after debugging on vscode:
[2, 4, 9, 11, 8, 3, 2, 5, 10]
Array length of numbers: 9
The 8 element of numbers is the 0 element of numbersrev
The 7 element of numbers is the 1 element of numbersrev
The 6 element of numbers is the 2 element of numbersrev
The 5 element of numbers is the 3 element of numbersrev
The 4 element of numbers is the 4 element of numbersrev
The 3 element of numbers is the 5 element of numbersrev
The 2 element of numbers is the 6 element of numbersrev
The 1 element of numbers is the 7 element of numbersrev
[10, 5, 2, 3, 8, 3, 2, 5, 10]
The top array is the original and the bottom array is the supposed reversal array
I cannot for the life of me find out why it stops changing the numbersrev array halfway through. Anybody know what the cause could be?

Okay, a few things...
First for loops increment their variables automatically in python.
so:
for k in range(8):
...
i -= 1
k += 1
should be:
for k in range(8):
...
i -= 1
No need to manually increment k.
Next lists are NOT arrays.
Lists in python are very different from arrays in a language like C.
Lists are mutable, and are passed by reference by default.
so when you try to make an empty array:
numbersrev = numbers #blank array for reverse
you are actually referencing the same 'list' from both numbers AND numbersrev
What you should have done is numbersrev = []
Then in your for loop, simply append to numbersrev rather than assign.
for k in range(numLength):
numbersrev.append(numbers[i])
print ("The ", i," element of numbers is the ", k," element of numbersrev")
i -= 1
Lastly
you could/should reference the length of numbers rather than a hardcoded value in your for loop, but how you have it will still work (assuming you ONLY ever get 8 numbers)
for k in range(numLength):
...
All together
numbers = read() #creates numbers array out of the txt file
numbersrev = [] #blank array for reverse
numLength = len(numbers) #measures the length of the array
print(numbers)
print("Array length of numbers: ", numLength)
i = numLength
i = i-1 #since the array starts at 0 instead of 1
for k in range(numLength):
numbersrev.append(numbers[i])
print ("The ", i," element of numbers is the ", k," element of numbersrev")
i -= 1
print(numbersrev)

numbersrev = numbers sets numbersrev to point to the same list as numbers, meaning when you modify numbers or numbersrev you're modifying the other at the same time. To make an actual copy of the object, you instead need to call numbersrev = numbers.copy(). Also, #sahasrara62's comment is correct, you need to call for k in range(numLength) instead of for k in range(8)

What you've done here is assign the reversed array as the normal array with this line:
numbersrev = numbers #blank array for reverse
What you're actually doing with that loop is this:
numbers[0] = numbers[9] # [10, 2, 3, 4, 5, 6, 7, 8, 9, 10]
numbers[1] = numbers[8] # [10, 9, 3, 4, 5, 6, 7, 8, 9, 10]
numbers[2] = numbers[7] # [10, 9, 8, 4, 5, 6, 7, 8, 9, 10]
numbers[3] = numbers[6] # [10, 9, 8, 7, 5, 6, 7, 8, 9, 10]
numbers[4] = numbers[5] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]
numbers[5] = numbers[4] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]
numbers[6] = numbers[3] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]
numbers[7] = numbers[2] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]
numbers[8] = numbers[1] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]
numbers[9] = numbers[0] # [10, 9, 8, 7, 6, 6, 7, 8, 9, 10]
...
If you assign the variable like this:
numLength = len(numbers) #measures the length of the array
numbersrev = [0]*numLength #blank array for reverse
You'll get the correct answer since the reverse list is no longer pointing to the normal list.

the problem you are facing is because of this line
numbersrev = numbers #blank array for reverse
In this line you are not creating an empty array, you are saving the reference of numbers array in a new variable named numbersrev. This means that when you make an operation in array numbersrev you are changing also the values of numbers. To avoid this kind of problems you have two options:
Make a copy of the array with slices
In this way you copy the values of the array, not the reference of the array. This means the changes you make to the new array will not change the original array.
numbersrev = numbers[:]
Create an empty array and use append instead of assignation
This change is a little different from what you did, but basically instead of creating a copy of the array, you create a new array which will be filled in the for loop, something like:
numbers.rev = []
...
for k in range(8):
numbersrev.append(numbers[i])
So with the first option and also changing some things in the k index we have a code like this:
numbers = [2, 4, 9, 11, 8, 3, 2, 5, 10] # you can change for read
numbersrev = numbers[:] #copy array elements
numLength = len(numbers) #array length
print(numbers)
print("Array length of numbers: ", numLength)
i = numLength - 1
# you don't need to initialize k because it's initialized and incremented with range in the loop
for k in range(numLength):
numbersrev[k] = numbers[i]
print ("The ", i," element of numbers is the ", k," element of numbersrev")
i -= 1
print(numbersrev)
Hope this would help you solve the problem, just like a note you could solve this problem in many ways: slicing (numbers[::-1]), list comprehension and some others. All the ways are valid so just in case you want to explore more.

Add 1 for odd numbers on list Python

So this is my code:
numbers = []#1
for i in range(10):
i += 1
numbers.append(i)
print (numbers)
numbers2 = [n + 2 for n in numbers]#2
print (numbers2)
numbers3 = []#3
for x in numbers2:
if (x % 2 == 1) :
x += 1
numbers3 = x
print (numbers3)
I'm using Google Colab and run those codes on 3 separate code cells(hashtag numbers comment). The #1 program output is [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]. And the #2 output is [3, 4, 5, 6, 7, 8, 9, 10, 11, 12]. So at #3 cell I want program to add 1 on each odd numbers in numbers2 list. The output I want is [4, 4, 6, 6, 8, 8, 10, 10, 12, 12]. But what I get is :
4
6
8
10
12
Also I'm trying to not use function(just for these codes). And for loop on #1 code I intend to do that.
Additional question : Is it possible to modify elements on list without append the result to another list(like #2 code)? Like just add 2 on each numbers on list

Try the following:
second_list = [3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
third_list = second_list
for i in range(len(second_list)):
if (second_list[i] % 2 == 1):
make_even = second_list[i] + 1
third_list[i] = make_even
else:
third_list[i] = second_list[i]
print (third_list)
You'll have to tweak it for the Google Colab project you're doing, but the logic here should be right. Right now this answer works in regular Python 3.

your third cell should look like this, you were close to the solution all you need to do is to add x values in numbers3 list
numbers3 = []#3
for x in numbers2:
if (x % 2 == 1) :
x += 1
numbers3.append(x)
print(numbers3)

In order to fill the list instead of just printing the value you must use the append function instead of =
numbers3 = x
#becomes
numbers3.append(x)
To get the list in the format you want, you also have to drop the append out of the if statement, and drop the print out of the for loop, like so:
numbers3 = []#3
for x in numbers2:
if (x % 2 == 1) :
x += 1
numbers3.append(x) # Here
print (numbers3) # and here

Single line chunk re-assignment

As shown in the following code, I have a chunk list x and the full list h. I want to reassign back the values stored in x in the correct positions of h.
index = 0
for t1 in range(lbp, ubp):
h[4 + t1] = x[index]
index = index + 1
Does anyone know how to write it in a single line/expression?
Disclaimer: This is part of a bigger project and I simplified the questions as much as possible. You can expect the matrix sizes to be correct but if you think I am missing something please ask for it. For testing you can use the following variable values:
h = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
x = [20, 21]
lbp = 2
ubp = 4

You can use slice assignment to expand on the left-hand side and assign your x list directly to the indices of h, e.g.:
h = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
x = [20, 21]
lbp = 2
ubp = 4
h[4 + lbp:4 + ubp] = x # or better yet h[4 + lbp:4 + lbp + len(x)] = x
print(h)
# [1, 2, 3, 4, 5, 6, 20, 21, 9, 10]
I'm not really sure why are you adding 4 to the indexes in your loop nor what lbp and ubp are supposed to mean, tho. Keep in mind that when you select a range like this, the list you're assigning to the range has to be of the same length as the range.

Edited aug 24 9pm - number game isn't working as I would like

I have a number guessing game working but I would like it to count without pick numbers without having them have any with a single increment. What I am trying to say is 2 4 17 27 not 2 3 4 17 27 I would like it to go through all the possibilities from low to high like it is, just not with any in a single increment IE 1 2 3 or 5 6.
I would also like it to be able to do from 1 to 100 and the count length to go to 10. If I try and put anymore than 6 in it will not work.
It gives me a result like this now
Please enter the lower limit: 2
Please enter the upper limit: 9
Please enter the number of values in sequences: 6
Possible sequences. Spot the missing one!
[2, 3, 4, 5, 6, 7] #I do not want it to have them all 1 digit up at a time
[2, 3, 4, 5, 6, 8] #like this
[2, 3, 4, 5, 6, 9]
[2, 3, 4, 5, 7, 8]
[2, 3, 4, 5, 7, 9]
[2, 3, 4, 5, 8, 9]
[2, 3, 4, 6, 7, 8]
[2, 3, 4, 6, 7, 9]
[2, 3, 4, 6, 8, 9]
[2, 3, 4, 7, 8, 9]
[2, 3, 5, 6, 7, 8]
[2, 3, 5, 6, 7, 9]
[2, 3, 5, 6, 8, 9]
[2, 3, 5, 7, 8, 9]
[2, 3, 6, 7, 8, 9]
Please enter the lower limit: 2
Please enter the upper limit: 13
Please enter the number of values in sequences: 6
[2, 4, 6, 8, 10] #I would like it more like this
[2, 4, 7, 9, 11] #so it go's through low to high but with out 1 digit
[2, 5, 7, 9, 11] #increments
[2, 5, 9, 11, 13]
[2, 6, 9, 11, 13]
[2, 7, 9, 11, 13,]
If anyone has any suggestions please let me know.
import itertools
import random
DEBUG = False
ALLOWED_GUESSES = 3
def get_game_parameters():
while True:
try:
lower_limit = int(input("Please enter the lower limit: "))
upper_limit = int(input("Please enter the upper limit: "))
consecutive_length = int(input("Enter The Number Limit For Consecutive Increments: "))
if lower_limit > upper_limit:
raise ValueError("Lower limit must not exceed upper limit")
sequence_length = int(input("Please enter the number of values in sequences: "))
if upper_limit - lower_limit < sequence_length:
raise ValueError("Difference in limits must be greater than sequence length")
except ValueError as e:
print("Invalid value entered:", e)
continue
else:
sequence_range = range(lower_limit, upper_limit + 2)
return sequence_range, sequence_length
###input ("Enter The Number Limit For Consecutive Increments: ")
def prompt_user_to_guess(chosen_sequence, required_sequence_length):
guesses_made = 0
while True:
try:
user_input = input(
"Please enter your guess for the hidden sequence, " +\
"separating terms by commas (e.g. '1, 2, 3, 4'): ")
guessed_sequence = [int(x) for x in user_input.split(",")]
if len(guessed_sequence) != required_sequence_length:
raise ValueError("Incorrect number of arguments")
except ValueError as e:
print("Invalid guess:", e)
continue
else:
guesses_made += 1
if guessed_sequence == chosen_sequence:
print("You guessed the correct sequence. Well done!")
return
elif guesses_made < ALLOWED_GUESSES:
remaining_guesses = ALLOWED_GUESSES - guesses_made
print("Incorrect guess! {} attempt(s) remaining.".format(remaining_guesses))
continue
else:
print("I'm sorry, you're out of guesses. The correct sequence was {}".format(chosen_sequence))
return
def generate_possible_sequences(sequence_range, sequence_length):
def is_monotonic_increasing(l):
return all(x < y for x, y in zip(l, l[1:]))
for permutation in itertools.permutations(sequence_range, sequence_length):
if is_monotonic_increasing(permutation):
yield list(permutation)
def main():
sequence_range, sequence_length = get_game_parameters()
possible_sequences = list(generate_possible_sequences(sequence_range, sequence_length))
chosen_sequence = possible_sequences.pop(random.randrange(len(possible_sequences)))
assert chosen_sequence not in possible_sequences
if DEBUG:
print("\nChosen sequence: {}".format(chosen_sequence))
print("\nPossible sequences. Spot the missing one!\n")
for sequence in possible_sequences:
print(sequence)
prompt_user_to_guess(chosen_sequence, sequence_length)
if __name__ == '__main__':
main()

I'm not clear on what exactly you are answering, and we need a better explanation of "it will not work". However, it looks like you generate far too many options in generate_possible_sequences() which probably results in either memory filling up or far too long an execution time. A better approach is to just shuffle numbers in range, then sort a sub-sequence, like so:
sequence_range, sequence_length = get_game_parameters()
vals = range(1, sequence_range + 1)
random.shuffle(vals)
chosen_sequence = sorted(vals[:sequence_length])
This will work almost instantly for sequence_range values well into the thousands, and you can step through it interactively to see how the code it working. However, for millions of elements (or just shorter code overall), the random.sample() function does what you want in just one line and without shuffling the complete list:
sequence_range, sequence_length = get_game_parameters()
chosen_sequence = sorted(random.sample(xrange(1, sequence_range + 1), sequence_length))
The xrange() here avoids creating an actual list in memory; this line gives an out of memory error:
random.sample(range(1, 999999999), 4)
This line works:
random.sample(xrange(1, 999999999), 4)
You probably also want:
guessed_sequence.sort()
This allows the user to input in any order.

Split list into dictionary

I am trying to split my list into a dictionary and I wrote a function for it. It takes in a list and gets the list length. If the length of the list is 253 , it creates a dictionary with 26 keys - this is calculated by rounding up the number to a higher 10 (250 will create 25 keys, 251-259 will create 26 keys). Each key will store a chuck of the original list (as of now I am storing 10 elements per list). I feel
def limit_files(file_list, at_a_time=10):
l = file_list
n = len(l)
d, r = divmod(n, at_a_time)
num_keys = d + 1 if r else d
slice = n // num_keys
vals = (l[i:i+slice] for i in range(0, n, slice+1))
dct = dict(zip(range(1,num_keys+1),vals))
return (dct)
I just wanted to know if there is way to improve the code

You can use itertools.izip_longest to group items in your list as equally divided chunks.
import itertools
def limit_files(file_list, at_a_time=10):
d, r = divmod(len(file_list), at_a_time)
num_keys = d + 1 if r > 0 else d
chunks = itertools.izip_longest(*([iter(x)] * at_a_time))
return dict((x, y) for x, y in enumerate(chunks))
Note that, it will be padding with None values to fill out the last chunk.
>>> limit_files([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12])
{0: (1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
1: (11, 12, None, None, None, None, None, None, None, None)}
Alternatively, without using padding values, you can just iterate through the range and call itertools.islice until the iterator exhausts as follows:
def limit_files(file_list, at_a_time=10):
d, r = divmod(len(file_list), at_a_time)
num_keys = d + 1 if r > 0 else d
iterator = iter(file_list)
dictionary = {}
for chunk_id in xrange(num_keys):
chunk = list(itertools.islice(iterator, at_a_time))
if not chunk:
break
dictionary[chunk_id] = chunk
return dictionary
>>> limit_files([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12])
{0: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 1: [11, 12]}