Exam PCAP topic 1 question 19 discussion

The answer will be A, D Why? dict = {'a': 1, 'b': None} # Works if 'a' in dict: print('yes') # Checks if the value is not None [The key could have value None] # Will fail for key 'b' as value is None # We have to cheque for if a key is present or not if dict['a'] != None: print('yes') print(dict['a'] != None) # AttributeError: 'dict' object has no attribute 'exists' # if dict.exists('a'): # print('yes') # Works if 'a' in dict.keys(): print('yes')

Correct: A,D dict={'Mom': 5551234567, 'Dad': 5557654321, "Son":None} print( dict.keys()) #dict_keys(['Mom', 'Dad', 'Son]) if 'Mom' in dict: print("Key exists") #ok if dict['Son'] != None : print("Key exists") #empty if dict.exists('Mom'): print("Key exists") #AttributeError: 'dict' object has no attribute 'exists' if 'Mom' in dict.keys(): print("Key exists") #ok

A,D C is not working at all B is checking if the value of key is different than None

A - is correct D - is correct B is can't be correct, as it checks value, not key

A is wrong - this takes the value, doesn't check if key exists

B fails in this particular case: dict = {"A1": 1, "A2": 2, "A3": 3, "A4": None} key = "A4" print(dict[key]!=None) So it's AD

Only A and D are correct. Technically there can be a key which has None as its value, then option B will fail, because it checks for the presence of a value, not the key itself. ######## sample code ######## d = {'key1': 1, 'key2': None} k = 'key2' print(d) if k in d: print(f'\'{k}\' exists in dict') else: print(f'\'{k}\' does not exist in dict') if k in d.keys(): print(f'\'{k}\' exists in dict') else: print(f'\'{k}\' does not exist in dict') # wrong way because it check for the presence of value, not the key itself if d.get(k) is not None: print(f'\'{k}\' exists in dict <-- using wrong way') else: print(f'\'{k}\' does not exist in dict <-- using wrong way') # wrong way because it check for the presence of value, not the key itself if d[k] != None: print(f'\'{k}\' exists in dict <-- using wrong way') else: print(f'\'{k}\' does not exist in dict <-- using wrong way')

3 of them work, I vote AD (B is a bit ugly!) dict = {'key': 'Farts'} try: if 'key' in dict: print("Key exists (A)") if dict['key']!= None: print("Key exists (B)") if 'key' in dict.keys(): print("Key exists (D)") if dict.exists ('key'): print("Key exists (C)") except: pass Key exists (A) Key exists (B) Key exists (D)

A&D are most Python. B also returns True but it's a check if a key isn't None and no if a key exists so I'd cut that answer first. > dict = {'key' : 'value'} > print('key' in dict) True > print(dict['key'] != None) True > print(dict.exists('key')) Traceback (most recent call last): File "./prog.py", line 4, in <module> AttributeError: 'dict' object has no attribute 'exists' > print('key' in dict.keys()) True

The only one that not works it is C, all the others works correctly.

A, B and D are rights!

'a' works also (there are a lot of mistakes in this website)

A. 'key' in dict D. 'key' in dict.keys ( )

the print statement looks like PYTHON 2!!!

A and D are the correct answers. B needs try/except.

A. 'key' in dict D. 'key' in dict.keys ( )

A, B & D are correct, but B checks if a key value is Not None. The most pythonic answer is A and D which checks the dictionary keys