如何重写$ x = $ hash {blah} || Python中的'default'？

Question

如何在不触发KeyError的情况下从Python字典中提取项目？在Perl中,我会这样做:

$x = $hash{blah} || 'default'

什么是等效的Python？

Answer 1

使用get(key, default)方法:

>>> dict().get("blah", "default")
'default'

Answer 2

如果你要做很多事情,最好使用collections.defaultdict:

import collections

# Define a little "factory" function that just builds the default value when called.
def get_default_value():
  return 'default'

# Create a defaultdict, specifying the factory that builds its default value
dict = collections.defaultdict(get_default_value)

# Now we can look up things without checking, and get 'default' if the key is unknown
x = dict['blah']