Write a Python program to move all spaces to the front of a given string in single traversal

def moveSpaces(str1): 
    no_spaces = [char for char in str1 if char!=' ']   
    space= len(str1) - len(no_spaces)
    # Create string with spaces
    result = ' '*space    
    return result + ''.join(no_spaces)
  
s1 = "Python Exercises"
print("Original String:\n",s1)

print("\nAfter moving all spaces to the front:")
print(moveSpaces(s1))