Reverse a String in Python

Reverse a string in Python

Using slicing:

>>> 'hello world'[::-1]
'dlrow olleh'

---

Slice notation takes the form [start:stop:step]. In this case, we omit the start and stop positions since we want the whole string. We also use step = -1, which means, "repeatedly step from right to left by 1 character".

How to reverse the words of a string considering the punctuation?

Try this (explanation in comments of code):

s = "Do or do not, there is no try."

o = []
for w in s.split(" "):
  puncts = [".", ",", "!"] # change according to needs
  for c in puncts:
    # if a punctuation mark is in the word, take the punctuation and add it to the rest of the word, in the beginning
    if c in w:
      w = c + w[:-1] # w[:-1] gets everthing before the last char
  
  o.append(w)
  

o = reversed(o) # reversing list to reverse sentence
print(" ".join(o)) # printing it as sentence


#output: .try no is there ,not do or Do

how to reverse a string in python without changing the position of words?

Just create a new empty str variable and concatenate it.

str5 = 'peter piper picked a peck of pickled peppers.'
b = str5.split()
rev_str5 = ""
for i in b:
    rev_str5 = rev_str5 + ' ' + i[::-1]
print(rev_str5.lstrip()) # Removes the one space in the starting.

Here's a shorter method too. Thanks for the comment:

str5 = 'peter piper picked a peck of pickled peppers.'    
print(' '.join(w[::-1] for w in str5.split()))

Output:

retep repip dekcip a kcep fo delkcip .sreppep

How do I reverse words in a string with Python

def reverseStr(s):
  return ' '.join([x[::-1] for x in s.split(' ')])

Reverse string without non letters symbol

You were really close! Your code is not working because you are applying the reversion to the whole string instead of doing it one word at a time. But just adding an extra step that splits the input string at white spaces (I assume white spaces is what defines words in your input) you'll get your desired result:

def reverse_string(st):
    return ' '.join(reverse_word(word) for word in st.split())

def reverse_word(st):
    stack = []
    for el in st:
        if el.isalpha():
            stack.append(el)
    result = ''
    for el in st:
        if el.isalpha():
            result += stack.pop()
        else:
            result += el
    return result

instr = 'b3ghcd hg#tyj%h'

print(reverse_string(instr)) # prints 'd3chgb hj#ytg%h'

---

NOTE:
You can pythonify your code a bit using some built in functions of list comprehension. In this case you'd replace the building of your stack.

stack = []
    for el in st:
        if el.isalpha():
            stack.append(el)

for one of the following:

stack = [el for el in st if el.isalpha()]
or
stack = list(filter(str.isalpha, st))

---

Related Topics