CODEWITHSUNDEEP
pythondictionary
Jay
Jay

Reputation: 23

Extract item from list of dictionaries using default values

I'd like to use list comprehension on the following list; 

movie_dicts = [
{'title':'A Boy and His Dog', 'year':1975, 'rating':6.6},
{'title':'Ran', 'year':1985, 'rating': 8.3},
{'year':2010, 'rating':8.0},
{'title':'Scanners', 'year':1981, 'rating': 6.7}
]

using my knowledge of list comprehension and dictionaries, I know that 

title_year = [i['title'] for i in movie_dicts]
print title_year

will print a list with movie titles. However as one of movie titles are missing i receive the following error

Traceback (most recent call last):
  File "./loadjson.py", line 30, in <module>
    title_year = [i['title'] for i in movie_dicts]
KeyError: 'title'

Is there any way of checking if the movie title exists placing a default value in its place if it doesn't?

Upvotes: 1

Views: 267

Answers (2)

Mohammed Aouf Zouag
Mohammed Aouf Zouag

Reputation: 17142

Use 

title_year = [i.get('title', 'defaultTitle') for i in movie_dicts]

It gives you the possibility to specify a default value if the specified key does not exist.

Upvotes: 3

Martijn Pieters
Martijn Pieters

Reputation: 1123490

Use the dict.get() method to return a default for missing keys:

title_year = [i.get('title', '<untitled>') for i in movie_dicts]

This substitutes the string '<untitled>' for missing titles. Alternatively, filter out entries without the key (producing a shorter list):

title_year = [i['title'] for i in movie_dicts if 'title' in i]

Upvotes: 4

Related Questions