Python Checking if a Dictionary is empty doesn t seem to work

Question

I am trying to check if a dictionary is empty but it doesn t behave properly  It just skips it and displays ONLINE without anything except of display the message  Any ideas why   def isEmpty self  dictionary       for element in dictionary          if element              return True         return False  def onMessage self  socket  message       if self isEmpty self users     False          socket send  quot Nobody is online  please use REGISTER command quot                      quot  in order to register into the server quot       else          socket send  quot ONLINE  quot         join self users keys

User · Answer

You can also use get    Initially I believed it to only check if key existed    gt  gt  gt  d      a  1   b  2   c       gt  gt  gt  bool d get  c    False  gt  gt  gt  d  c    e   1  gt  gt  gt  bool d get  c    True   What I like with get is that it does not trigger an exception  so it makes it easy to traverse large structures

User · Answer

test dict      if not test dict keys        print  quot Dict is Empty quot

User · Answer

Empty dictionaries evaluate to False in Python    gt  gt  gt  dct       gt  gt  gt  bool dct  False  gt  gt  gt  not dct True  gt  gt  gt    Thus  your isEmpty function is unnecessary   All you need to do is   def onMessage self  socket  message       if not self users          socket send  Nobody is online  please use REGISTER command                          in order to register into the server       else          socket send  ONLINE          join self users keys

User · Answer

A dictionary can be automatically cast to boolean which evaluates to False for empty dictionary and True for non-empty dictionary    if myDictionary  non empty clause   else  empty clause     If this looks too idiomatic  you can also test len myDictionary  for zero  or set myDictionary keys    for an empty set  or simply test for equality with        The isEmpty function is not only unnecessary but also your implementation has multiple issues that I can spot prima-facie    The return False statement is indented one level too deep  It should be outside the for loop and at the same level as the for statement  As a result  your code will process only one  arbitrarily selected key  if a key exists  If a key does not exist  the function will return None  which will be cast to boolean False  Ouch  All the empty dictionaries will be classified as false-nagatives   If the dictionary is not empty  then the code will process only one key and return its value cast to boolean  You cannot even assume that the same key is evaluated each time you call it  So there will be false positives    Let us say you correct the indentation of the return False statement and bring it outside the for loop  Then what you get is the boolean OR of all the keys  or False if the dictionary empty  Still you will have false positives and false negatives  Do the correction and test against the following dictionary for an evidence    myDictionary  0  zero       Empty string   None  None value   False  Boolean False value       Empty tuple

User · Answer

dict      print len dict keys       if length is zero means that dict is empty

User · Answer

Here are three ways you can check if dict is empty  I prefer using the first way only though  The other two ways are way too wordy   test dict       if not test dict      print  Dict is Empty    if not bool test dict       print  Dict is Empty    if len test dict     0      print  Dict is Empty

User · Answer

Simple ways to check an empty dict are below           a          1  if a                   print   empty dict       2  if not a             print   empty dict     Although method 1st is more strict as when a   None  method 1 will provide correct result but method 2 will give an incorrect result

User · Answer

use  any    dict       if any dict            true        dictionary is not empty   else           false         dictionary is empty

[python] Python: Checking if a 'Dictionary' is empty doesn't seem to work

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