CODEWITHSUNDEEP
pythondictionary
Joe Gagliardi
Joe Gagliardi

Reputation: 131

Appending to a list in a dictionary

I've been attempting to add a value to the end of a list inside a dictionary using a different dictionary. The assignment is a little more complicated, so I have simplified the problem down to these three lines, but keep getting None as a result.

finley = {'a':0, 'b':2, 'c':[41,51,61]}
crazy_sauce = {'d':3}
print finley['c'].append(crazy_sauce['d'])

Upvotes: 7

Views: 22624

Answers (4)

Aaditya Ura
Aaditya Ura

Reputation: 12689

Your solution is correct, but :

Most functions, methods that change the items of sequence/mapping does return None: list.sort, list.append, dict.clear.

So just use print dict in next line after you update the list in dict. 

finley = {'a':0, 'b':2, 'c':[41,51,61]}
crazy_sauce = {'d':3}
finley['c'].append(crazy_sauce['d'])
print(finley)

Upvotes: 1

MarianD
MarianD

Reputation: 14201

The append() method changes the list in-place - it doesn't create and then return the changed (extended) list, it doesn't return anything (which in Python means that it returns the None special value).

So you first change your nested list in-place (not assigning it to other variable):

finley['c'].append(crazy_sauce['d'])

and then print the changed outer directory:

print(finley)

Upvotes: 0

Erick Shepherd
Erick Shepherd

Reputation: 1443

You are attempting to print the return value of the .append() function, which is None. You need to print the dict value after the call to .append(), like so:

finley      = {'a':0, 'b':2, 'c':[41, 51 ,61]}
crazy_sauce = {'d':3}

finley['c'].append(crazy_sauce['d'])

print(finley['c'])

Where the output is the following list:

[41, 51, 61, 3]

Upvotes: 1

Sandeep Lade
Sandeep Lade

Reputation: 1943

Your code is fine but print finley['c'].append(crazy_sauce['d']) prints none since finley['c'].append(crazy_sauce['d']) returns none. you remove print here and add a print finley['c'] in next line

finley = {'a':0, 'b':2, 'c':[41,51,61]}
crazy_sauce = {'d':3}
finley['c'].append(crazy_sauce['d'])
print finley['c']

Upvotes: 6

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