Dictionary
- Python Dictionary For Loop Generate Keys Youtube
- Python Dictionary Iterate Keys
- Dictionary Python For Loop
- Python Dictionary For Loop Generate Keys In Word
- Python For Loop Key Value
Populating a dictionary using for loops (python) duplicate. Add a print statement in the second for loop – Ajay May 16 '15. How can I add new keys to a. Python: How to Sort a Dictionary by key or Value? Different ways to Iterate / Loop over a Dictionary in Python; Different ways to Remove a key from Dictionary in Python del vs dict.pop Python: 6 Different ways to create Dictionaries; Python Pandas: How to create DataFrame from dictionary? Python: How to get all keys with maximum value. Mar 01, 2018 Python How to iterate Dictionary Key and Value pairs loop. 08 Beginner's Guide to Python - Dictionaries and For Loops - Duration: 10:32. London App Developer 14,222 views.
- Python Add keys to nested dictionary Addition of keys in dictionaries have been discussed many times, but sometimes, we might have a problem in which we require to alter/add keys in the nested dictionary.
- In this article, we show how to iterate through all keys of a dictionary in Python. So, say, we have a dictionary. This can be any dictionary. A dictionary contains key-value pairs. Each key contains a value. Let's say, however, that we don't want the values of the keys in this particular instance. We just want the keys.
- Note that the restriction with keys in Python dictionary is only immutable data types. Python Split dictionary of lists to list of dictionaries. Generate link.
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.
Example
Create and print a dictionary:
thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
print(thisdict)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
print(thisdict)
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:
Try it Yourself »There is also a method called
get()
that will give you the same result:Example
Get the value of the 'model' key:
Try it Yourself »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
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict['year'] = 2018
Loop Through a Dictionary
![Loop Loop](/uploads/1/2/6/0/126064196/957419962.png)
You can loop through a dictionary by using a
for
loop.Python Dictionary For Loop Generate Keys Youtube
When looping through a dictionary, the return value are the keys of the dictionary, but there are methods to return the values as well.
Example
Print all key names in the dictionary, one by one:
Try it Yourself »Example
Print all values in the dictionary, one by one:
Try it Yourself »Example
You can also use the
Try it Yourself »values()
function to return values of a dictionary:Example
Loop through both keys and values, by using the
Try it Yourself »items()
function:Check if Key Exists
To determine if a specified key is present in a dictionary use the
in
keyword: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')
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
if 'model' in thisdict:
print('Yes, 'model' is one of the keys in the thisdict dictionary')
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:
Python Dictionary Iterate Keys
Try it Yourself »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)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict['color'] = 'red'
print(thisdict)
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)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict.pop('model')
print(thisdict)
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)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict.popitem()
print(thisdict)
Example
The
del
keyword removes the item with the specified key name: thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
del thisdict['model']
print(thisdict)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
del thisdict['model']
print(thisdict)
Example
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.
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
del thisdict
print(thisdict) #this will cause an error because 'thisdict' no longer exists.
Example
The
clear()
method empties the dictionary: thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict.clear()
print(thisdict)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
thisdict.clear()
print(thisdict)
Copy a Dictionary
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()
.Example
Make a copy of a dictionary with the
copy()
method: thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
mydict = thisdict.copy()
print(mydict)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
mydict = thisdict.copy()
print(mydict)
Another way to make a copy is to use the built-in method
dict()
.Dictionary Python For Loop
Example
Make a copy of a dictionary with the
dict()
method: thisdict = {
'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
mydict = dict(thisdict)
print(mydict)
Try it Yourself »'brand': 'Ford',
'model': 'Mustang',
'year': 1964
}
mydict = dict(thisdict)
print(mydict)
Nested Dictionaries
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
}
}
Try it Yourself »'child1' : {
'name' : 'Emil',
'year' : 2004
},
'child2' : {
'name' : 'Tobias',
'year' : 2007
},
'child3' : {
'name' : 'Linus',
'year' : 2011
}
}
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
}
Try it Yourself »'name' : 'Emil',
'year' : 2004
}
child2 = {
'name' : 'Tobias',
'year' : 2007
}
child3 = {
'name' : 'Linus',
'year' : 2011
}
myfamily = {
'child1' : child1,
'child2' : child2,
'child3' : child3
}
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)
Try it Yourself »# note that keywords are not string literals
# note the use of equals rather than colon for the assignment
print(thisdict)
Python Dictionary For Loop Generate Keys In Word
Dictionary Methods
Python has a set of built-in methods that you can use on dictionaries.
Python For Loop Key Value
Method | Description |
---|---|
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 |