One line if-condition-assignment

Question

I have the following code  num1   10 someBoolValue   True   I need to set the value of num1 to 20 if someBoolValue is True  and do nothing otherwise  So  here is my code for that  num1   20 if someBoolValue else num1   Is there someway I could avoid the    else num1 part to make it look cleaner  An equivalent to   if someBoolValue      num1   20   I tried replacing it with    else pass like this  num1 20 if someBoolValue else pass  All I got was syntax error  Nor I could just omit the    else num1 part

User · Answer

num1   20   someBoolValue or num1

User · Answer

For the future time traveler from google  here is a new way  available from python 3 8 onward    b   1 if a    b        this section is only reached if b is not 0 or false        Also  a is set to b     print a  b

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Another way num1    20 boolVar   num1  not boolVar

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You can do it this way   try      a    i for i in  20  if False  0  except IndexError      print  Do what ever you want here     You can solve your problem this way but  using  try except block  is not the best practice for python

User · Answer

No  I guess you were hoping that something like num1   20 if someBoolValue would work  but it doesn t  I think the best way is with the if statement as you have written it   if someBoolValue      num1   20

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Use this   num1   20 if someBoolValue else num1

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you can use one of the following    falseVal  trueVal  TEST   TEST and trueVal or falseVal

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num1   10   10  someBoolValue is True    That s my new final answer  Prior answer was as follows and was overkill for the stated problem  Getting too clever    not Good   Here s the prior answer    still good if you want add one thing for True cond and another for False   num1   10    0 10  someBoolValue is True    You mentioned num1 would already have a value that should be left alone   I assumed num1   10 since that s the first statement of the post  so the operation to get to 20 is to add 10   num1   10 someBoolValue   True  num1   10    0 10  someBoolValue is True   print f num1    num1  nsomeBoolValue    someBoolValue      produced this output  num1   20 someBoolValue   True

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If one line code is definitely going to happen for you  Python 3 8 introduces assignment expressions affectionately known as    the walrus operator              someBoolValue and  num    20    The 20 will be assigned to num if the first boolean expression is True  The assignment must be inside parentheses here otherwise you will get a syntax error   num   10 someBoolValue   True  someBoolValue and  num    20  print num    20  num   10 someBoolValue   False  someBoolValue and  num    20  print num    10

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You can definitely use num1    20 if someBoolValue else num1  if you want

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In one line   if someBoolValue  num1   20   But don   t do that  This style is normally not expected  People prefer the longer form for clarity and consistency   if someBoolValue      num1   20    Equally  camel caps should be avoided  So rather use some bool value    Note that an in-line expression some value if predicate without an else part does not exist because there would not be a return value if the predicate were false  However  expressions must have a clearly defined return value in all cases  This is different from usage as in  say  Ruby or Perl

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Here is what i can suggest   Use another variable to derive the if clause and assign it to num1   Code   num2  20 if someBoolValue else num1 num1 num2

User · Answer

I don t think this is possible in Python  since what you re actually trying to do probably gets expanded to something like this   num1   20 if someBoolValue else num1   If you exclude else num1  you ll receive a syntax error since I m quite sure that the assignment must actually return something   As others have already mentioned  you could do this  but it s bad because you ll probably just end up confusing yourself when reading that piece of code the next time   if someBoolValue  num1 20   I m not a big fan of the num1   someBoolValue and 20 or num1 for the exact same reason  I have to actually think twice on what that line is doing   The best way to actually achieve what you want to do is the original version   if someBoolValue      num1   20   The reason that s the best verison is because it s very obvious what you want to do  and you won t confuse yourself  or whoever else is going to come in contact with that code later   Also  as a side note  num1   20 if someBoolValue is valid Ruby code  because Ruby works a bit differently

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If you wish to invoke a method if some boolean is true  you can put else None to terminate the trinary      gt  gt  gt  a 1  gt  gt  gt  print a  if a  1 else None 1  gt  gt  gt  print a  if a  2 else None  gt  gt  gt  a 2  gt  gt  gt  print a  if a  2 else None 2  gt  gt  gt  print a  if a  1 else None  gt  gt  gt

[python] One line if-condition-assignment

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