title: Flatten a nested list of strings into a single string
body: <p>I am trying to convert a list of list into a single string using python and I don't want to use any loops I want to do it using lambda in Python but not getting the desired result.
  here is my code:</p>
  
  <pre><code>#!/usr/bin/python
  import sys
  import math
  from functools import reduce
  def collapse(L):
      list = lambda L: [item for sublist in L for item in sublist]
      #sum(L, [])
      #print('"',*list,sep=' ')
      #whole_string = ''.join(list).replace(' ')
  l=[ ["I","am"], ["trying", "to", "convert"], ["listoflist", "intoastring."]]
  collapse(l)
  print(*l,sep='')
  </code></pre>
  
  <p>I want an output like this "I am  trying to convert listoflist intoastring."</p>