Iterating through list of list in Python

Question

I want to iterate through list of list  I want to iterate through irregularly nested lists inside list also  Can anyone let me know how can I do that   x    u sam      Test      one               u file txt     id   1  0        Test2         u file2 txt     id   1  2

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x    u sam      Test      one               u file txt     id   1  0        Test2         u file2 txt     id   1  2           output       def lister l       for item in l          if type item  in  list  tuple  set               lister item          else              output append item   lister x

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two nested for loops    for a in x       print  --------------       for b in a               print b   It would help if you gave an example of what you want to do with the lists

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If you wonder to get all values in the same list you can use the following code   text    u sam      Test      one               u file txt     id   1  0        Test2         u file2 txt     id   1  2            def get values lVals       res          for val in lVals          if type val  not in  list  set  tuple               res append val          else              res extend get values val       return res  get values text

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So wait  this is just a list-within-a-list   The easiest way is probably just to use nested for loops    gt  gt  gt  a     1  3  4    2  4  4    3  4  5    gt  gt  gt  a   1  3  4    2  4  4    3  4  5    gt  gt  gt  for list in a          for number in list              print number     1 3 4 2 4 4 3 4 5   Or is it something more complicated than that  Arbitrary nesting or something  Let us know if there s something else as well   Also  for performance reasons  you might want to look at using list comprehensions to do this   http   docs python org tutorial datastructures html nested-list-comprehensions

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This traverse generator function can be used to iterate over all the values   def traverse o  tree types  list  tuple        if isinstance o  tree types           for value in o              for subvalue in traverse value  tree types                   yield subvalue     else          yield o  data     1 1  1 1  1  1      1 1 1   1   1  1  1   1       print list traverse data     prints  1  1  1  1  1   1   1  1  1  1  1  1  1   1    for value in traverse data       print repr value    prints   1   1   1   1   1    1    1   1   1   1   1   1   1    1

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It sounds like you need to use recursion   Make a function to iterate through a list  and if it hits an item that is also a list  call itself to iterate on the member   Here s a link to something similar   http   www saltycrane com blog 2008 08 python-recursion-example-navigate-tree-data

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if you don t want recursion you could try   x    u sam      Test      one               u file txt     id   1  0        Test2         u file2 txt     id   1  2           layer1 x layer2    while True      for i in layer1          if isinstance i list               for j in i                  layer2 append j          else              print i     layer1    layer2     layer2        if len layer1   0          break   which gives   sam Test Test2  u file txt     id   1  0    u file2 txt     id   1  2   one    note that it didn t look into the tuples for lists because the tuples aren t lists  You can add tuple to the  isinstance  method if you want to fix this

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This can also be achieved with itertools chain from iterable which will flatten the consecutive iterables   import itertools for item in itertools chain from iterable iterables         do something with item

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Create a method to recursively iterate through nested lists  If the current element is an instance of list  then call the same method again  If not  print the current element  Here s an example   data    1 2 3  4  5 6 7  8 9      def print list the list        for each item in the list          if isinstance each item  list               print list each item          else              print each item   print list data

[python] Iterating through list of list in Python

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