Python List Generator Of Dict With Specific Keys
Python List Generator Of Dict With Specific Keys 4,4/5 1900 reviews
  1. Python List Generator Of Dict With Specific Keys Free
  2. Python Dict Keys Values
  3. Python List Of Dict Keys
  4. Python List Generator Of Dict With Specific Keys Download
  5. Python List Generator Of Dict With Specific Keys In Math

Dictionary

A dictionary is a collection which is unordered, changeable and indexed. In Python dictionaries are written with curly brackets, and they have keys and values.

Python dictionary method keys returns a list of all the available keys in the dictionary. Following is the syntax for keys method − dict.keys Parameters. Return Value. This method returns a list of all the available keys in the dictionary. The following example shows the usage of keys method. By default, the keys within a python dictionary are unsorted and the output of the json.dumps function may be different when executing multiple times. I ran into this issue while writing some test cases, but setting the sortkeys parameter to true will solve the problem. This will sort the key values of the dictionary and will produce always the same output when using the same data. A dictionary is a collection which is unordered, changeable and indexed. In Python dictionaries are written with curly brackets, and they have keys and values. Class typing.TypedDict (dict) ¶ A simple typed namespace. At runtime it is equivalent to a plain dict. TypedDict creates a dictionary type that expects all of its instances to have a certain set of keys, where each key is associated with a value of a consistent type. This expectation is not checked at runtime but is only enforced by type checkers.

Example

Create and print a dictionary:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
print(thisdict)
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Accessing Items

You can access the items of a dictionary by referring to its key name, inside square brackets:

Example

Get the value of the 'model' key:

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There is also a method called get() that will give you the same result:

Example

Get the value of the 'model' key:

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Change Values

You can change the value of a specific item by referring to its key name:

Example

Change the 'year' to 2018:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict['year'] = 2018
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Loop Through a Dictionary

You can loop through a dictionary by using a for loop.

When looping through a dictionary, the return value are the keys of the dictionary, but there are methods to return the values as well.

Python List Generator Of Dict With Specific Keys Free

Example

Print all key names in the dictionary, one by one:

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Example

Print all values in the dictionary, one by one:

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Example

You can also use the values() function to return values of a dictionary:

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Example

Loop through both keys and values, by using the items() function:

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Check if Key Exists

To determine if a specified key is present in a dictionary use the in keyword: Product key office 2010 plus.

Example

Check if 'model' is present in the dictionary:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
if 'model' in thisdict:
print('Yes, 'model' is one of the keys in the thisdict dictionary')
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Dictionary Length

To determine how many items (key-value pairs) a dictionary has, use the len() method.

Example

Print the number of items in the dictionary:

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Adding Items

Adding an item to the dictionary is done by using a new index key and assigning a value to it:

Example

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict['color'] = 'red'
print(thisdict)
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Removing Items

There are several methods to remove items from a dictionary:

Example

The pop() method removes the item with the specified key name:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict.pop('model')
print(thisdict)
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Example

The popitem() method removes the last inserted item (in versions before 3.7, a random item is removed instead):

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict.popitem()
print(thisdict)
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Example

The del keyword removes the item with the specified key name:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
del thisdict['model']
print(thisdict)
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Example

Dict

The del keyword can also delete the dictionary completely:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
del thisdict
print(thisdict) #this will cause an error because 'thisdict' no longer exists.
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Example

The clear() method empties the dictionary:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict.clear()
print(thisdict)
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Copy a Dictionary

Python Dict Keys Values

You cannot copy a dictionary simply by typing dict2 = dict1, because: dict2 will only be a reference to dict1, and changes made in dict1 will automatically also be made in dict2.

There are ways to make a copy, one way is to use the built-in Dictionary method copy().

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Example

Make a copy of a dictionary with the copy() method:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
mydict = thisdict.copy()
print(mydict)
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Another way to make a copy is to use the built-in method dict().

Example

Make a copy of a dictionary with the dict() method:

thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
mydict = dict(thisdict)
print(mydict)
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Nested Dictionaries

Python List Of Dict Keys

A dictionary can also contain many dictionaries, this is called nested dictionaries.

Example

Create a dictionary that contain three dictionaries:

myfamily = {
'child1' : {
'name' : 'Emil',
'year' : 2004
},
'child2' : {
'name' : 'Tobias',
'year' : 2007
},
'child3' : {
'name' : 'Linus',
'year' : 2011
}
}
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Or, if you want to nest three dictionaries that already exists as dictionaries:

Example

Create three dictionaries, than create one dictionary that will contain the other three dictionaries:

child1 = {
'name' : 'Emil',
'year' : 2004
}
child2 = {
'name' : 'Tobias',
'year' : 2007
}
child3 = {
'name' : 'Linus',
'year' : 2011
}
myfamily = {
'child1' : child1,
'child2' : child2,
'child3' : child3
}
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The dict() Constructor

It is also possible to use the dict() constructor to make a new dictionary:

Example

thisdict = dict(brand='Ford', model='Mustang', year=1964)
# note that keywords are not string literals
# note the use of equals rather than colon for the assignment
print(thisdict)
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Dictionary Methods

Python List Generator Of Dict With Specific Keys Download

Python has a set of built-in methods that you can use on dictionaries.

MethodDescription
clear()Removes all the elements from the dictionary
copy()Returns a copy of the dictionary
fromkeys()Returns a dictionary with the specified keys and value
get()Returns the value of the specified key
items()Returns a list containing a tuple for each key value pair
keys()Returns a list containing the dictionary's keys
pop()Removes the element with the specified key
popitem()Removes the last inserted key-value pair
setdefault()Returns the value of the specified key. If the key does not exist: insert the key, with the specified value
update()Updates the dictionary with the specified key-value pairs
values()Returns a list of all the values in the dictionary

Python List Generator Of Dict With Specific Keys In Math

P: n/a
And there may be more complex list(vector like 3 or 4 dimentional data
structure), is there any easy method to tackle this problem?
Any suggestions are welcome!
Best regards,
Davy
On Nov 6, 4:50 pm, Davy <[email protected]:
Hi Matimus and Boris,
Thank you :)
And a further question about vector above rank 1, how can I use it as
the key of dictionary?
For example, if I have list like L=[[1,2,3],[4,5,6,7]],
Then I do L_tuple = tuple(L)>>L_tuple = ([1,2,3],[4,5,6,7])
But {L_tuple:'hello'} cause an error?
Best regards,
Davy
On Nov 6, 3:09 pm, Matimus <[email protected]:
On Nov 5, 10:53 pm, Davy <[email protected]:
Hi all,
We know that list cannot be used as key of dictionary. So, how to work
around it?
For example, there is random list like l=[1,323,54,67].
Any suggestions are welcome!
Best regards,
Davy
Use a tuple instead.
>>d = {}
>>d[tuple([1,2,3,4])] = 'hello world'
>>d
{(1, 2, 3, 4): 'hello world'}>>d[1,2,3,4]
'hello world'
Matt- Hide quoted text -

- Show quoted text -