Check if value already exists within list of dictionaries

Question

I ve got a Python list of dictionaries  as follows   a           main color    red    second color   blue          main color    yellow    second color   green          main color    yellow    second color   blue        I d like to check whether a dictionary with a particular key value already exists in the list  as follows      is a dict with  main color   red  in the list already     if not  add item

User · Answer

Maybe this helps   a       main color    red    second color   blue            main color    yellow    second color   green            main color    yellow    second color   blue     def in dictlist  key  value   my dictlist       for this in my dictlist          if this key     value              return this     return     print in dictlist   main color   red    a  print in dictlist   main color   pink    a

User · Answer

Based on  Mark Byers great answer  and following  Florent question  just to indicate that it will also work with 2 conditions on list of dics with more than 2 keys   names      names append   first    Nil    last    Elliot    suffix    III    names append   first    Max    last    Sam    suffix    IX    names append   first    Anthony    last    Mark    suffix    IX     if not any d  first       Anthony  and d  last       Mark  for d in names        print  Not exists    else      print  Exists      Result   Exists

User · Answer

Here s one way to do it  if not any d  main color       red  for d in a         does not exist  The part in parentheses is a generator expression that returns True for each dictionary that has the key-value pair you are looking for  otherwise False   If the key could also be missing the above code can give you a KeyError  You can fix this by using get and providing a default value  If you don t provide a default value  None is returned  if not any d get  main color   default value      red  for d in a         does not exist

User · Answer

Following works out for me         usr bin env python     a       main color    red    second color   blue           main color    yellow    second color   green           main color    yellow    second color   blue         found event   next              filter                  lambda x  x  main color       red                   a                       return this dict when not found             dict                  name  red                   value                                   if found event          print found event        python   tmp x       main color    red    second color    blue

User · Answer

Perhaps a function along these lines is what you re after    def add unique to dict list dict list  key  value     for d in dict list       if key in d          return d key     dict list append   key  value      return value

[python] Check if value already exists within list of dictionaries?

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