for loop with two variables

Question

How can I include two variables in the same for loop   t1    a list of integers  strings and lists  t2    another list of integers  strings and lists   def f t     a function that will read lists  t1  and  t2  and return all elements that are identical     for i in range len t1   and for j in range len t2

User · Answer

For your use case  it may be easier to utilize a while loop   t1    137  42  t2     Hello    world    i   0 j   0 while i  lt  len t1  and j  lt  len t2       print t1 i   t2 j      i    1     j    1    137 Hello   42 world   As a caveat  this approach will truncate to the length of your shortest list

User · Answer

I think you are looking for nested loops    Example  based on your edit    t1  1 2  Hello   1 2  999 1 23  t2  1  Hello   1 2  999   t3     for it1  e1 in enumerate t1       for it2  e2 in enumerate t2           if e1  e2              t3 append  it1 it2 e1      t3   0  0  1    2  1   Hello     3  2   1  2     4  3  999     Which can be reduced to a single comprehension     it1 it2 e1  for it1  e1 in enumerate t1  for it2  e2 in enumerate t2  if e1  e2     But to find the common elements  you can just do   print set t1   amp  set t2    set   1  2   1   Hello   999     If your list contains non-hashable objects  like other lists  dicts  use a frozen set   from collections import Iterable s1 set frozenset e1  if isinstance e1 Iterable  else e1 for e1 in t1  s2 set frozenset e2  if isinstance e2 Iterable  else e2 for e2 in t2  print s1  amp  s2

User · Answer

for  i j  in   i j  for i in range x  for j in range y     should do it

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Python 3    Add 2 vars with for loop using zip and range  Returning a list   Note  Will only run till smallest range ends    gt  gt  gt a  g h for g h in zip range 10   range 10     gt  gt  gt a  gt  gt  gt  0  2  4  6  8  10  12  14  16  18

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If you want the effect of a nested for loop  use   import itertools for i  j in itertools product range x   range y          Stuff      If you just want to loop simultaneously  use   for i  j in zip range x   range y          Stuff      Note that if x and y are not the same length  zip will truncate to the shortest list   As  abarnert pointed out  if you don t want to truncate to the shortest list  you could use itertools zip longest   UPDATE  Based on the request for  a function that will read lists  t1  and  t2  and return all elements that are identical   I don t think the OP wants zip or product   I think they want a set   def equal elements t1  t2       return list set t1  intersection set t2          You could also do       return list set t1   amp  set t2     The intersection method of a set will return all the elements common to it and another set  Note that if your lists contains other lists  you might want to convert the inner lists to tuples first so that they are hashable  otherwise the call to set will fail     The list function then turns the set back into a list   UPDATE 2  OR  the OP might want elements that are identical in the same position in the lists   In this case  zip would be most appropriate  and the fact that it truncates to the shortest list is what you would want  since it is impossible for there to be the same element at index 9 when one of the lists is only 5 elements long    If that is what you want  go with this   def equal elements t1  t2       return  x for x  y in zip t1  t2  if x    y    This will return a list containing only the elements that are the same and in the same position in the lists

User · Answer

There s two possible questions here  how can you iterate over those variables simultaneously  or how can you loop over their combination   Fortunately  there s simple answers to both  First case  you want to use zip   x    1  2  3  y    4  5  6   for i  j in zip x  y      print str i            str j     will output  1   4 2   5 3   6   Remember that you can put any iterable in zip  so you could just as easily write your exmple like   for i  j in zip range x   range y          do work here    Actually  just realised that won t work  It would only iterate until the smaller range ran out  In which case  it sounds like you want to iterate over the combination of loops   In the other case  you just want a nested loop   for i in x      for j in y          print str i            str j     gives you  1   4 1   5 1   6 2   4 2   5       You can also do this as a list comprehension    str i            str j  for i in range x  for j in range y     Hope that helps

User · Answer

If you really just have lock-step iteration over a range  you can do it one of several ways   for i in range x     j   i         or for i  j in enumerate range x            or for i  j in   i i  for i in range x            All of the above are equivalent to for i  j in zip range x   range y   if x  lt   y   If you want a nested loop and you only have two iterables  just use a nested loop   for i in range x     for i in range y             If you have more than two iterables  use itertools product   Finally  if you want lock-step iteration up to x and then to continue to y  you have to decide what the rest of the x values should be   for i  j in itertools zip longest range x   range y   fillvalue float  nan             or for i in range min x y      j   i       for i in range min x y   max x y      j   float  nan

User · Answer

Any reason you can t use a nested for loop   for i in range x      for j in range y           code that uses i and j

[python] "for loop" with two variables?

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