I am attempting to iterate over a list of integers and to join them based on a condition using the python standard library. For example, I have a list of integers that looks as such:

listOfIntegers = [0, 0, 0, 2, 0, 4, 6, 0, 8, 0, 0, 0, 1, 9]

I would like to iterate through this list and combine values such that the result would be a string of the form:

result = '000-20-4-60-8000-1-9'

(where the dashes are included). The condition for this is that if the preceding number is not equal to zero a dash must be placed in front of it. If the next value is equal to zero it is joined to the end of the value before it.

CodePudding user response：

This would help: (Considering numbers are positive in the given list)

def join(lst):
    return "".join(list(map(lambda x: str(-x), lst))).lstrip('-')

listOfIntegers = [0, 0, 0, 2, 0, 4, 6, 0, 8, 0, 0, 0, 1, 9]
print(join(listOfIntegers)) # 000-20-4-60-8000-1-9

The process:

1. Convert each element to negative, in which:
   • 9 becomes -9
   • 0 has no effect as -0 is 0 in python
2. Then convert them into strings and join them
3. Make sure to remove Trailing hyphen, in our case lstrip('-') helps us with that.

CodePudding user response：

A straightforward approach, building a string from the list of integers, followed by a simple regex replacement:

listOfIntegers = [1, 0, 0, 2, 0, 4, 6, 0, 8, 0, 0, 0, 1, 9]
inp = ''.join([str(x) for x in listOfIntegers])
result = re.sub(r'(?<=.)(?=[^\D0])', '-', inp)
print(result)  # 100-20-4-60-8000-1-9

CodePudding user response：

Here is a simple solution:

listOfIntegers = [0, 0, 0, 2, 0, 4, 6, 0, 8, 0, 0, 0, 1, 9]

for i in listOfIntegers:
    if i != 0:
        print("-"   str(i), end="")
    else:
        print(str(i), end="")

For each item in the list, we check if the item is not equal to 0. If it isn't equal to 0, we print out the item with a dash in front of it, and use the end parameter to avoid new lines. If it is 0, we simply print out the item.

CodePudding user response：

Using a loop:

def func(nums):
    result = ''
    for num in nums:
        if num != 0:
            result  = '-'
        result  = str(num)
    return result