Reverse a Sentence and String Compression - Python

Reverse a Sentence and String Comprehension with same logic in Python 3

Reverse a Sentence

Solution 1: Using Split & Reverse

def reversed_sentence(a):
  return " ".join(reversed(a.split()))

Solution 2: Using Split and Index

def reversed_sentence2(a):
  return " ".join(a.split()[::-1])

Solution 3: Without using inbuilt functions | Double While Loop

def reversed_sentence3(a):
  words = []
  length = len(a)
  i = 0
  while i<length:
    if a[i] != " ":
      word_start = i
      while i<length and a[i] != " ":
        i+=1
      words.append(a[word_start:i])
    i+=1
  return " ".join(reversed(words))

Test

%timeit reversed_sentence("Hello World! How are you?")
935 ns per loop
%timeit reversed_sentence2("Hello World! How are you?")
710 ns per loop
%timeit reversed_sentence3("Hello World! How are you?")
5.54 µs per loop

String Compression - AAABBBCCDEeeEaaBB to A3B3C2DEe2Ea2B2

def compress_string(s):

  compress = []

  i=0

  length = len(s)

  while i < length:

    letter = s[i]

    count = 0

    while i < length and letter==s[i]:

      count+=1

      i+=1

    if count == 1:

      compress.append(letter)

    else:

      compress.append(letter+str(count))

  return "".join(compress)

Test

%timeit compress_string("AAABBBCCDEeeEaaBB")

6.98 µs per loop

compress_string("AAABBBCCDEeeEaaBB")

'A3B3C2DEe2Ea2B2'