File Reading

[toxicxarrow]

This assignment is technically complete according to my instructions, but I would like to polish it up a bit for my own learning experience. Basically, I was tasked to display 15 numbers in a file, then calculate the average of said numbers.

# Initialize constants
total = 0
lines = 0
file = 0
average = 0

# Gather all numbers in file for display
with open('numbers.dat', 'r') as file:
    lines = file.read()

# Add all numbers in file
for add in open('numbers.dat'):
    total += int(add.strip())

# Calculate the average of numbers in file
average = total / 15
average = round(average, 2)

#Print all numbers in file
print('The numbers in the file are:')
print(lines)

# Print the average of numbers in file
print('The average of those numbers is:')
print(average)

# Close file
file.close()

# END #

Question 1:
In this line of code:

# Calculate the average of numbers in file
average = total / 15
average = round(average, 2)

How can I replace the "15" with the number of integers that are actually in the file? Say I wanted to put 20 numbers in there instead of 15 to calculate the average, I'd like the total to be divided by the amount of numbers there are, not just a constant.

Question 2: What can I add to ignore spaces in the file, and only use the numbers on each line? The code works fine if the numbers are in a nice column without any spaces; however, I get an error if there is a single space in between the numbers.

Please keep any suggestions as close to the initial code as possible, and thank you for reading this far.

Cheers.

[ThiefOfTime]

How are the numbers laying in the file? If there is a number for each line then you get the integers by getting the lines. if you have multiple numbers per line this would be a slightly different approach. I will assume that there is just a single number in each line, else please correct me :)
lets say you have red the lines of the file to the variable lines. now you could to this:

lines = [int(line.strip()) for line in lines if not line.strip == " "]

if you now say len(lines) you get the number of integers in your file.
if you have the numbers seperated by " " then think about splitting them using line.split(" ")
a little excerpt of you data would help :)

[wavic]

sum_ = 0
numbers = 0
for line in lines:
    try:
        sum_ += int(line)
        numbers += 1
    except ValueError:
        pass

I am assuming that list comprehension is not allowed so here is one way to do it. It's readable and clear.

I just have learned something new. Stripping whitespace characters is not necessary to convert a string to an integer. I tried it couple of minutes ago.

>>> int('  \t10 \n')
10

[killerrex]

To keep the code as similar as possible to yours, you can use:

# Add all numbers in file
n = 0
for add in open('numbers.dat'):
    total += int(add.strip())
    n += 1
 
# Calculate the average of numbers in file
average = total / n

But your code has many things to improve:
- It opens the file twice for no reason
- Initialises variables when is not needed (the only one needed is 'total')
- The last file.close() is redundant as the with block guarantees that the file is closed at exit.

The same in a more pythonic way:

# Notice that this will fail if there is a blank line in your input file
with open('numbers.dat', 'rt') as fd:
    numbers = [int(s.strip()) for s in fd]

average = round(sum(numbers) / len(numbers), 2)

print('The numbers in the file are:')
for n in numbers:
    print(n)
 
# Print the average of numbers in file
print('The average of those numbers is:')
print(average)

And you shall add also guards in case the file is empty to avoid dividing by 0 when you calculate the average.

[toxicxarrow]

Thank you guys so much for your help. I literally learned something new from every response.

@ ThiefOfTime You are correct, the file is just a column of random numbers, single integer per row. The instructor will grade with his own data file, which is why I was looking to skip spaces in the off chance there were spaces in his file.

Again, thank you guys for the help!

---

@killerrex Quick question, why does this line:

numbers = [int(s.strip()) for s in file]

only accept brackets [] around the command, and it won't accept ()?

[killerrex]

In that form is just to create a list, as the [x for x in xxx] is a syntactic sugar for list(x for x in xxx).
In particular the part of "x for x in xxx" produces a generator, that you can pass it to any place in python that accepts a generator as input (behaves as the command "range")

The other 2 "pretty" syntax similar to that one is to create a set or a dictionary:

# Imagine fd contains 1, 2, 555, 44
# You only want the different numbers, no matter the repetitions => Create set of numbers
>>> {int(s.strip()) for s in fd}
{1, 2, 555, 44}

# You want to create a dictionary initialising the entry to something
>>> {int(s.strip()): 'xxx' for s in fd}
{1: 'xxx', 2: 'xxx', 44: 'xxx', 555: 'xxx'}

# If you want to create a tuple you can do it with:
>>> tuple(int(s.strip()) for s in fd)
(1, 2, 44, 555)

[wavic]

As I'm looking at the assignment, they are not likely to passed the generators.

[toxicxarrow]

@killerrex Wow, I didn't even realize doing it like that made the whole thing a list! Super nifty! TY for the explanation.

@wavic You're right, we definitely didn't learn about generators yet. This is my first Python class, so it's pretty lightweight. In fact, it mostly focuses on pseudocode, which is why I am asking what may seem like such easy solutions to you guys.

[wavic]

We've all gone trough this. No one speaks Python at the age of one and a half

[toxicxarrow]

Thanks, man! Definitely something I'm glad you said. :)