However, neither a list nor any other dictionary can be used as dictionary keys because lists and dictionaries are editable: Technical Note: The .items(), .keys(), and .values() methods actually return something called a view object. A dictionary display object is more or less similar to a window containing keys and values. For convenience, you can think of these methods as rollover lists of keys and dictionary values. Above, uppercase is a dictionary object that contains key-value pairs in { }. The left side of: is a key and the right side is a value. The key must be unique and an immutable object. A number, string, or tuple can be used as a key. Therefore, the following dictionaries are also valid: Once you define a dictionary, you can display its contents as you can for a list. The above three definitions are displayed as follows: You can check whether or not a paritular key exists in a dictionary collection by using the in keywords or not, as shown below. Note that only keys are searched for, not values.

The keys() method returns an object that contains a list of keys in the dictionary. The following defines a dictionary that maps a location to the name of the corresponding Major League Baseball team: You can use the in operator with short circuit evaluation to avoid an error when you try to access a key that is not in the dictionary: This example demonstrates another function of dictionaries: The values in the dictionary do not have to be of the same type. Personally, some values are strings, one is an integer, one is a list, and one is another dictionary. In fact, iterating through all keys is the default behavior when iterating through a dictionary. Therefore, you do not need to use the keys() method. However, a dictionary with a list as a key is not valid because the list is editable: The popitem() method can be used to delete and return any pair of items (key, value) from the dictionary. All items can be deleted at once using the clear() method. 11.

Which of the following statements does not apply to dictionary keys? a) More than one key is not allowed b) Keys must be immutable c) Keys must be integers d) If duplicate keys are found, the last assignment wins Show response When you run this code, the list of dictionaries must be printed without Charlie. NameError indicates that the dictionary object has been removed from memory. Because of this difference, lists and dictionaries are generally suitable for different circumstances. You should now have a good idea of what, if anything, would be best suited for a particular situation. Returns true if the key in the dictionary dict; false otherwise, Second, a dictionary key must be of an immutable type. You`ve already seen examples where some of the immutable types you know (Integer, Float, String, and Boolean) have served as dictionary keys. A dictionary in Python is the unordered, editable collection of data values that contains key-value pairs. Each key-value pair in the dictionary maps the key to its associated value, optimizing it. A dictionary in Python is declared by including a comma-separated list of key/value pairs with braces ({}).

Python Dictionary is divided into two elements: keys and values. The People Dictionary has five key-value pairs that represent first name, last name, age, favorite colors, and active status. You can also sort items in the dictionary. For example, if we want to print the names of the items in our dictionary in alphabetical order, we must use the for loop. Each item in the dictionary is sorted accordingly. To add a new key-value pair to a dictionary, specify the name of the dictionary followed by the new key in square brackets with the new value. You can delete individual dictionary items or delete the entire contents of a dictionary. You can also delete the entire dictionary in a single operation. Produces a printable string representation of a dictionary a) {1: `A`, 2: `B`, 3: `C`} b) C c) {1:3, 2:3, 3:3} d) There is no method called setdefault() for the dictionary Show response Python`s built-in hash() function returns the hash value of an object that can be hashed and throws an exception for an object. This is not the case: A value is extracted from a dictionary by specifying the corresponding key in square brackets ([]): First, a given key can appear only once in a dictionary. Duplicate keys are not allowed.

A dictionary assigns each key to a corresponding value, so it doesn`t make sense to assign a particular key more than once.