Example use of continue statement in Python

Question

The definition of the continue statement is       The continue statement continues with the next iteration of the loop    I can t find any good examples of code    Could someone suggest some simple cases where continue is necessary

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def filter out colors elements     colors     red    green     result        for element in elements      if element in colors         continue   skip the element       You can do whatever here     result append element    return result     gt  gt  gt  filter out colors   lemon    orange    red    pear        lemon    orange    pear

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It is not absolutely necessary since it can be done with IFs but it s more readable and also less expensive in run time   I use it in order to skip an iteration in a loop if the data does not meet some requirements     List of times at which git commits were done    Formatted in hour  minutes in tuples    Note the last one has some fantasy  commit times     8 20    9 30    11  45    15  50    17  45    27  132    for time in commit times      hour   time 0      minutes   time 1         If the hour is not between 0 and 24       and the minutes not between 0 and 59 then we know something is wrong        Then we don t want to use this value        we skip directly to the next iteration in the loop      if not  0  lt   hour  lt   24 and 0  lt   minutes  lt   59           continue        From here you know the time format in the tuples is reliable        Apply some logic based on time      print  Someone commited at  h   m   format h hour  m minutes     Output   Someone commited at 8 20 Someone commited at 9 30 Someone commited at 11 45 Someone commited at 15 50 Someone commited at 17 45   As you can see  the wrong value did not make it after the continue statement

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I like to use continue in loops where there are a lot of contitions to be fulfilled before you get  down to business   So instead of code like this   for x  y in zip a  b       if x  gt  y          z   calculate z x  y          if y - z  lt  x              y   min y  z              if x    2 - y    2  gt  0                  lots                   of                   code                   here     I get code like this   for x  y in zip a  b       if x  lt   y          continue     z   calculate z x  y      if y - z  gt   x          continue     y   min y  z      if x    2 - y    2  lt   0          continue     lots       of       code       here     By doing it this way I avoid very deeply nested code  Also  it is easy to optimize the loop by eliminating the most frequently occurring cases first  so that I only have to deal with the infrequent but important cases  e g  divisor is 0  when there is no other showstopper

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For example if you want to do diferent things depending on the value of a variable   my var   1 for items in range 0 100       if my var  lt  10          continue     elif my var    10          print  hit       elif my var  gt  10          print  passed       my var   my var   1   In the example above if I use break the interpreter will skip the loop  But with continueit only skips the if-elif statements and go directly to the next item of the loop

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Let s say we want to print all numbers which are not multiples of 3 and 5  for x in range 0  101       if x   3   0 or x   5    0          continue          no more code is executed  we go to the next number      print x

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Here is very good visual representation about continue and break statements  source

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import random    for i in range 20         x   random randint -5 5        if x    0  continue       print 1 x     continue is an extremely important control statement  The above code indicates a typical application  where the result of a division by zero can be avoided  I use it often when I need to store the output from programs  but dont want to store the output if the program has crashed  Note  to test the above example  replace the last statement with print 1 float x   or you ll get zeros whenever there s a fraction  since randint returns an integer  I omitted it for clarity

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Here s a simple example  for letter in  Django           if letter     D           continue     print  quot Current Letter   quot    letter   Output will be  Current Letter  j Current Letter  a Current Letter  n Current Letter  g Current Letter  o  It continues to the next iteration of the loop

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Usually the situation where continue is necessary useful  is when you want to skip the remaining code in the loop and continue iteration   I don t really believe it s necessary  since you can always use if statements to provide the same logic  but it might be useful to increase readability of code

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continue simply skips the rest of the code in the loop until next iteration

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Some people have commented about readability  saying  Oh it doesn t help readability that much  who cares    Suppose you need a check before the main code   if precondition fails message   continue      main code here       Note you can do this after the main code was written without changing that code in anyway   If you diff the code  only the added line with  continue  will be highlighted since there are no spacing changes to the main code     Imagine if you have to do a breakfix of production code  which turns out to simply be adding a line with continue   It s easy to see that s the only change when you review the code   If you start wrapping the main code in if else  diff will highlight the newly indented code  unless you ignore spacing changes  which is dangerous particularly in Python   I think unless you ve been in the situation where you have to roll out code on short notice  you might not fully appreciate this

[python] Example use of "continue" statement in Python?

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