Why is the loop not calculating every lowercase letter from a string?-CodePudding

I am trying to calculate every lowercase letter from a mixed uppercase and lowercase string and form a new string of only lowercase. For example I have a string named st="ABcASFatBD" and I expect an output of low= "cat" but I am getting only "c" as the output. Below is my code.

    class Solution(object):

    def find_crowd(self, st):
        lo = ""
        for i in range(len(st)):

            if st[i].islower():
                lo  = st[i]
                return lo
            else:
                pass


if __name__ == "__main__":
    p = Solution()
    s = "ABcASFatBD"
    print(p.find_crowd(s))

CodePudding user response：

The problem is that you have your script ending on the first time it finds a lowercase value, whereas your return lo should be outside of the for i in range(...):. But heres a simpler version of your code:

class Solution(object):

    def find_crowd(self, st):
        lo = ""
        lo = ''.join([char for char in st if char.islower() == True])
        return lo


if __name__ == "__main__":
    p = Solution()
    s = "ABcASFatBD"
    print(p.find_crowd(s))

Hope this helps

CodePudding user response：

The problem with your code is that you call return statement in your if statement which ends the loop without passing through the end of your string.

class Solution(object):
  def find_crowd(self, st):
    lo = ""
    for i in range(len(st)):
      if st[i].islower():
        lo  = st[i]
    return lo


if __name__ == "__main__":
  p = Solution()
  s = "ABcASFatBD"
  print(p.find_crowd(s))

You can also convert your string into a list of characters before iterating on it and getting an individual element. You can convert a string into a list using [*s]. Just see the output of the print below to understand. Here is the simplest way to do that:

class Solution(object):
  def find_crowd(self, st):
    lo = ""
    for i in [*st]:
      if i.islower():
        lo  = i
    return lo


if __name__ == "__main__":
  p = Solution()
  s = "ABcASFatBD"
  print([*s])
  print(p.find_crowd(s))

CodePudding user response：

Your function is returning when first lowercase character is obtained.!

Some solutions are:-

class Solution(object):

    def find_crowd(self, st):
        lo=""
        for i in range(len(st)):
            if st[i].islower():
                lo  = st[i]
        return lo


if __name__ == "__main__":
    p = Solution()
    s = "ABcASFatBD"
    print(p.find_crowd(s))

Using ord() function [Ascii Values]:-

class Solution(object):
    def find_crowd(self, st):
        lo=""
        for i in st:
            if ord(i)>=97 and ord(i)<=122:
                lo  = i
        return lo


if __name__ == "__main__":
    p = Solution()
    s = "ABcASFatBDZzaA"
    print(p.find_crowd(s))

One liner [Pythonic Way]:-

class Solution(object):
    def find_crowd(self, st):
        return "".join([lower for lower in st if lower.islower() == True])


if __name__ == "__main__":
    p = Solution()
    s = "ABcASFatBDZzaA"
    print(p.find_crowd(s))