Why dict.get(key) instead of dict[key]?

Question

Today, I came across the dict method get which, given a key in the dictionary, returns the associated value.

For what purpose is this funct

Answer 1

Why dict.get(key) instead of dict[key]?

0. Summary

Comparing to dict[key], dict.get provides a fallback value when looking up for a key.

1. Definition

get(key[, default]) 4. Built-in Types — Python 3.6.4rc1 documentation

Return the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a KeyError.

d = {"Name": "Harry", "Age": 17}
In [4]: d['gender']
KeyError: 'gender'
In [5]: d.get('gender', 'Not specified, please add it')
Out[5]: 'Not specified, please add it'

2. Problem it solves.

If without default value, you have to write cumbersome codes to handle such an exception.

def get_harry_info(key):
    try:
        return "{}".format(d[key])
    except KeyError:
        return 'Not specified, please add it'
In [9]: get_harry_info('Name')
Out[9]: 'Harry'
In [10]: get_harry_info('Gender')
Out[10]: 'Not specified, please add it'

As a convenient solution, dict.get introduces an optional default value avoiding above unwiedly codes.

3. Conclusion

dict.get has an additional default value option to deal with exception if key is absent from the dictionary