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Python 'for word in word' loop

Basic for a loop, I need help to understand how these loop words are:

word = "hello"
for word in word:
  print word

Was the variable overwritten word=hello

with a word=h

just after starting the for loop? If so, how does it still go through all the letters in the word string?

Thanks in advance for the clarification.

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2 answers


Let's look at the bytecode:

>>> def so25807731():
...   word = "hello"
...   for word in word:
...     print word
... 
>>> import dis
>>> dis.dis(so25807731)
  2           0 LOAD_CONST               1 ('hello')
              3 STORE_FAST               0 (word)

  3           6 SETUP_LOOP              19 (to 28)
              9 LOAD_FAST                0 (word)
             12 GET_ITER            
        >>   13 FOR_ITER                11 (to 27)
             16 STORE_FAST               0 (word)

  4          19 LOAD_FAST                0 (word)
             22 PRINT_ITEM          
             23 PRINT_NEWLINE       
             24 JUMP_ABSOLUTE           13
        >>   27 POP_BLOCK           
        >>   28 LOAD_CONST               0 (None)
             31 RETURN_VALUE

Note that Python first grabs the iterator for string ( GET_ITER

) and then iterates over that, not the actual string ( FOR_ITER

).



Therefore, the original string is not required to "remember" what the characters were; it just uses the newly created iterator to do this. The value "old word

" is no longer used, so you can overwrite it without problems. This kind of logic explains why this code might work as well:

word = "llamas"
for character in word:
  word = None
  print character
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i have never coded python but i think it will work like this



word = "hello"
i=0
while i <len(word):
     print word[i]
     i += 1
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