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How to create a list with all values being zero - Printable Version

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How to create a list with all values being zero - 357mag - Jul-13-2019

I've written a program that asks the user to input integers which will be placed in a list. I only want to input four integers. I'm looking for ways to make my list all zeros. Doesn't appear that this is as intuitive as arrays are in C++. Anyway this is what I got:

numbers = [0] * 4

index = 0

while index < 4:
    numbers[index] = int(input("Enter a value for the list: "))
    index += 1

print("\nHere is the values you entered: ", end='')

for i in numbers:
    print(str(i) + " ", end='')

print()
print()
According to my book the repetition operator makes multiple copies of a list and then it joins them all together. So is it doing numbers[0] + numbers[0] + numbers[0] + numbers[0] to finally get numbers[0, 0, 0, 0]?

Isn't there an easier way to initialize all elements to zero?


RE: How to create a list with all values being zero - ichabod801 - Jul-13-2019

First, I'm not sure what's so hard about numbers = [0] * 4. That seems like an easy way to initialize a list to zeros. Second of all, you don't need to do that, since you are overwriting all the values anyway. In Python, lists do not have a set size, their size can change. The Pythonic way to get a list of four integers from the user is:

numbers = []
for number in range(4):
    numbers.append(int(input('Enter a value for the list: ')))

print('\nHere are the values you entered: {}.'.format(', '.join(str(number) for number in numbers)))



RE: How to create a list with all values being zero - 357mag - Jul-14-2019

When I tried the numbers [] the program threw an error message. So I presumed you cannot create a list that way.


RE: How to create a list with all values being zero - snippsat - Jul-14-2019

numbers = [] is the preferred way in Python,do you get error when run @ichabod801 code?
# Using literals [],the prefered way
>>> numbers = []
>>> numbers
[]
>>> numbers.append(0)
>>> numbers
[0]
>>> numbers.append(99)
>>> numbers
[0, 99]
 
>>> # Function object list()
>>> numbers = list()
>>> numbers
[]

>>> # No need initialize list as may do in other langues as C/C++
>>> numbers = [0] * 4
>>> numbers
[0, 0, 0, 0]
If only shall display numbers in a string i would keep it as string,and only convert to int() if needed.
numbers = []
for number in range(4):
    numbers.append(input('Enter a value for the list: '))

print(f"\nHere are the values you entered: {','.join(numbers)}.")
Output:
λ python num.py Enter a value for the list: 10 Enter a value for the list: 0 Enter a value for the list: 0 Enter a value for the list: 999 Here are the values you entered: 10,0,0,999.



RE: How to create a list with all values being zero - ThomasL - Jul-14-2019

(Jul-14-2019, 07:20 AM)357mag Wrote: When I tried the numbers [] the program threw an error message. So I presumed you cannot create a list that way.
Instead of whining around what about showing the error your program threw?
numbers []
will definitely throw an error because you need to write
numbers = []