Django templates If false

Question

How do I check if a variable is False using Django template syntax      if myvar    False      Doesn t seem to work   Note that I very specifically want to check if it has the Python value False  This variable could be an empty array too  which is not what I want to check for

User · Answer

In old version you can only use the ifequal or ifnotequal     ifequal YourVariable ExpectValue          Do something here     endifequal      Example      ifequal userid 1      Hello No 1    endifequal        ifnotequal username  django       You are not django     else      Hi django     endifnotequal      As in the if tag  an    else    clause is optional   The arguments can be hard-coded strings  so the following is valid      ifequal user username  adrian                endifequal    An alternative to the ifequal tag is to use the if tag and the    operator   ifnotequal Just like ifequal  except it tests that the two arguments are not equal   An alternative to the ifnotequal tag is to use the if tag and the    operator   However  now we can use if else easily     if somevar  gt   1       endif        if  bc  in  abcdef       This appears since  bc  is a substring of  abcdef     endif      Complex expressions  All of the above can be combined to form complex expressions  For such expressions  it can be important to know how the operators are grouped when the expression is evaluated - that is  the precedence rules  The precedence of the operators  from lowest to highest  is as follows    or and not in            lt       lt         More detail  https   docs djangoproject com en dev ref templates builtins

User · Answer

Django 1 10  release notes  added the is and is not comparison operators to the if tag  This change makes identity testing in a template pretty straightforward   In 2   from django template import Context  Template  In 3   context   Context   somevar   False   zero   0    In 4   compare false   Template     if somevar is False   is false   endif      In 5   compare false render context  Out 5   u is false   In 6   compare zero   Template     if zero is not False   not false   endif      In 7   compare zero render context  Out 7   u not false    If You are using an older Django then as of version 1 5  release notes  the template engine interprets True  False and None as the corresponding Python objects   In 2   from django template import Context  Template  In 3   context   Context   is true   True   is false   False                              is none   None   zero   0    In 4   compare true   Template     if is true    True   true   endif      In 5   compare true render context  Out 5   u true   In 6   compare false   Template     if is false    False   false   endif      In 7   compare false render context  Out 7   u false   In 8   compare none   Template     if is none    None   none   endif      In 9   compare none render context  Out 9   u none    Although it does not work the way one might expect   In 10   compare zero   Template     if zero    False   0    False   endif      In 11   compare zero render context  Out 11   u 0    False

User · Answer

Just ran into this again  certain I had before and came up with a less-than-satisfying solution    For a tri-state boolean semantic  for example  using models NullBooleanField   this works well      if test passed lower     false            endif      Or if you prefer getting excited over the whole thing        if test passed upper     FALSE            endif      Either way  this handles the special condition where you don t care about the None  evaluating to False in the if block  or True case

User · Answer

This is far easier to check in Python  i e  your view code  than in the template  because the Python code is simply   myvar is False   Illustrating    gt  gt  gt  False is False True  gt  gt  gt  None is False False  gt  gt  gt     is False False   The problem at the template level is that the template if doesn t parse is  though it does parse in    Also  if you don t mind it  you could try to patch support for is into the template engine  base it on the code for

User · Answer

For posterity  I have a few NullBooleanFields and here s what I do   To check if it s True      if variable   True   endif      To check if it s False  note this works because there s only 3 values -- True False None       if variable    None   False   endif      To check if it s None      if variable    None   None   endif      I m not sure why  but I can t do variable    False  but I can do variable    None

User · Answer

I think this will work for you      if not myvar

User · Answer

I ve just come up with the following which is looking good in Django 1 8  Try this instead of value is not False   if value stringformat  r      False    Try this instead of value is True   if value stringformat  r      True    unless you ve been really messing with repr methods to make value look like a boolean I reckon this should give you a firm enough assurance that value is True or False

User · Answer

Look at the yesno helper  Eg      myValue yesno  itwasTrue itWasFalse itWasNone

User · Answer

You could write a custom template filter to do this in a half-dozen lines of code   from django template import Library  register   Library     register filter def is false arg        return arg is False   Then in your template      if myvar is false         endif      Of course  you could make that template tag much more generic    but this suits your needs specifically  -

User · Answer

I have had this issue before  which I solved by nested if statements first checking for none type separately      if object some bool    None   Empty    else      if not object some bool   False   else   True   endif      endif      If you only want to test if its false  then just     if some bool    None      else      if not some bool   False   endif      endif      EDIT  This seems to work      if 0    a length   Zero-length array   else      if a    None   None type   else      if not a   False type   else   True-type    endif      endif      endif      Now zero-length arrays are recognized as such  None types as None types  falses as False  Trues as trues  strings arrays above length 0 as true   You could also include in the Context a variable false list    False   and then do      if some bool in false list   False    endif

[django] Django templates: If false?

In old version you can only use the ifequal or ifnotequal

Example:

However, now we can use if/else easily

Complex expressions

More detail

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