How to iterate over each string in a list of strings and operate on it s elements

Question

Im new to python and i need some help with this   TASK   given a list --    words     aba    xyz    xgx    dssd    sdjh    i need to compare the first and the last element of each string in the list   if the first and the last element in the string is the same   then increment the count   Given list is    words     aba    xyz    xgx    dssd    sdjh     If i try manually  i can iterate over each element of the strings in the list   words     aba    xyz    xgx    dssd    sdjh   w1   words 0  print w1 aba  for i in w1     print i  a b a  if w1 0     w1 len w1  - 1      c    1    print c  1   But  When i try to iterate over all the elements of all the strings in the list   using a FOR loop   i get an error   words     aba    xyz    xgx    dssd    sdjh   c   0 for i in words       w1   words i       if w1 0     w1 len w1  - 1          c    1      print c   ERROR   Traceback  most recent call last     File   lt stdin gt    line 2  in  lt module gt  TypeError  list indices must be integers  not str   please let me know  how would i achieve comparing the first and the last element of a no  strings in the list   Thanks in advance

User · Answer

for i j in enumerate words     i---index of word----j       now you got index of your words  present in i       print i

User · Answer

c 0 words     challa   reddy   challa    for idx  word in enumerate words       if idx  0          firstword word         print firstword      elif idx    len words -1          lastword word         print lastword          if firstword  lastword              c c 1             print c

User · Answer

You are iterating trough items in words but you have to iterate through item s length  words     aba    xyz    xgx    dssd    sdjh   c   0 for i in range len words        w1   words i      if w1 0     w1 len w1  - 1         c    1     print  c    In your case i 0  is  aba  because i is calculated from items in words  words     aba    xyz    xgx    dssd    sdjh   c   0 for i in words  print i    the output is   aba

User · Answer

The following code outputs the number of words whose first and last letters are equal  Tested and verified using a python online compiler   words     aba    xyz    xgx    dssd    sdjh     count   0   for i in words         if i 0   i -1           count   count   1   print count      Output    python main py 3

User · Answer

The reason is that in your second example i is the word itself  not the index of the word  So  for w1 in words       if w1 0     w1 len w1  - 1          c    1      print c   would the equivalent of your code

User · Answer

The suggestion that using range len    is the equivalent of using enumerate   is incorrect  They return the same results  but they are not the same   Using enumerate   actually gives you key value pairs  Using range len    does not   Let s check range len    first  working from the example from the original poster    words     aba    xyz    xgx    dssd    sdjh       print range len words     This gives us a simple list    0  1  2  3  4        and the elements in this list serve as the  indexes  in our results   So let s do the same thing with our enumerate   version   words     aba    xyz    xgx    dssd    sdjh          print enumerate words    This certainly doesn t give us a list    lt enumerate object at 0x7f6be7f32c30 gt       so let s turn it into a list  and see what happens   print list enumerate words     It gives us     0   aba     1   xyz     2   xgx     3   dssd     4   sdjh      These are actual key value pairs   So this      words     aba    xyz    xgx    dssd    sdjh    for i in range len words        print  words         format i   words i        actually takes the first list  Words   and creates a second  simple list of the range indicated by the length of the first list   So we have two simple lists  and we are merely printing one element from each list in order to get our so-called  key value  pairs   But they aren t really key value pairs  they are merely two single elements printed at the same time  from different lists   Whereas the enumerate    code   for i  word in enumerate words       print  words           format i  word        also creates a second list  But that list actually is a list of key value pairs  and we are asking for each key and value from a single source -- rather than from two lists  like we did above    So we print the same results  but the sources are completely different -- and handled completely differently

User · Answer

Try   for word in words      if word 0     word -1           c    1     print c   for word in words returns the items of words  not the index  If you need the index sometime  try using enumerate   for idx  word in enumerate words       print idx  word   would output  0   aba  1   xyz  etc    The -1 in word -1  above is Python s way of saying  the last element   word -2  would give you the second last element  and so on   You can also use a generator to achieve this   c   sum 1 for word in words if word 0     word -1

User · Answer

Use range   instead  like the following    for i in range len words

[python] How to iterate over each string in a list of strings and operate on it's elements

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