Core Python Programming (2nd Edition)

dict2['arch'] = 'sunos5' # add new entry
>>>
>>> print 'host %(name)s is running on port %(port)d' %
dict2
host venus is running on port 6969
If the key does exist, then its previous value will be overridden by its new value. The print statement
above illustrates an alternative way of using the string format operator ( % ), specific to dictionaries.
Using the dictionary argument, you can shorten the print request somewhat because naming of the
dictionary occurs only once, as opposed to occurring for each element using a tuple argument.
You may also add the contents of an entire dictionary to another dictionary by using the update() builtin
method. We will introduce this method in Section 7.4.
How to Remove Dictionary Elements and Dictionaries
Removing an entire dictionary is not a typical operation. Generally, you either remove individual
dictionary elements or clear the entire contents of a dictionary. However, if you really want to "remove"
an entire dictionary, use the del statement (introduced in Section 3.5.5). Here are some deletion
examples for dictionaries and dictionary elements:
del dict2['name'] # remove entry with key 'name'
dict2.clear() # remove all entries in dict1
del dict2 # delete entire dictionary
dict2.pop('name') # remove & return entry w/key
Core Tip: Avoid using built-in object names as identifiers for
variables!
For those of you who began traveling in the Python universe before
version 2.3, you may have once used dict as an identifier for a
dictionary. However, because dict() is now a type and factory
function, overriding it may cause you headaches and potential bugs.
The interpreter will allow such overriding-hey, it thinks you seem
smart and look like you know what you are doing! So be careful. Do
NOT use variables named after built-in types like: dict, list, file,
bool, str, input, or len!