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Python: Find the first non-repeating character in given string

Python String: Exercise-51 with Solution

Write a Python program to find the first non-repeating character in given string.

Sample Solution:-

Python Code:

def first_non_repeating_character(str1):
  char_order = []
  ctr = {}
  for c in str1:
    if c in ctr:
      ctr[c] += 1
    else:
      ctr[c] = 1 
      char_order.append(c)
  for c in char_order:
    if ctr[c] == 1:
      return c
  return None

print(first_non_repeating_character('abcdef'))
print(first_non_repeating_character('abcabcdef'))
print(first_non_repeating_character('aabbcc'))

Sample Output:

a
d
None              

Pictorial Presentation:

Python String: Find the first non-repeating character in given string
Python String: Find the first non-repeating character in given string

Flowchart:

Flowchart: Find the first non-repeating character in given string

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Previous: Write a Python program to split a string on the last occurrence of the delimiter.
Next:Write a Python program to print all permutations with given repetition number of characters of a given string

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Python: Tips of the Day

What is the difference between Python's list methods append and extend?

append: Appends object at the end.

x = [1, 2, 3]
x.append([4, 5])
print (x)

Output:

[1, 2, 3, [4, 5]]

extend: Extends list by appending elements from the iterable.

x = [1, 2, 3]
x.extend([4, 5])
print (x)

Output:

[1, 2, 3, 4, 5]

Ref: https://bit.ly/2AZ6ZFq