Dictionaries in Python

Python Dictionary:

Dictionaries are Python’s implementation of a data structure that is more generally known as an associative array. A dictionary consists of a collection of key-value pairs. Each key-value pair maps the key to its associated value.Keys are unique within a dictionary while values may not be.

Creating a dictionary:

Each key is separated from its value by a colon (:), the items are separated by commas, and the whole thing is enclosed in curly braces. An empty dictionary without any items is written with just two curly braces, like this: {}.

The values of a dictionary can be of any type, but the keys must be of an immutable data type such as strings, numbers, or tuples.Dictionary keys are case sensitive, same name but different cases of Key will be treated distinctly.

Creating a dictionary

Output:

If we attempt to access a data item with a key, which is not part of the dictionary, we get an error as follows −

creating dictionary output
Dictionary can also be created by the built-in function dict(). An empty dictionary can be created by just placing to curly braces{}.

Using built-in function dict()

Output:

using built-in function dict() output

Nested Dictionary:

Using nested dictionary

Adding elements to a Dictionary:

In Python Dictionary, Addition of elements can be done in multiple ways. One value at a time can be added to a Dictionary by defining value along with the key e.g. Dict[Key] = ‘Value’. Updating an existing value in a Dictionary can be done by using the built-in update() method. Nested key values can also be added to an existing Dictionary.While adding a value, if the key value already exists, the value gets updated otherwise a new Key with the value is added to the Dictionary.

Adding elements to a Dictionary

Output:

Adding elements to a Dictionary output

Accessing elements from a Dictionary:

In order to access the items of a dictionary refer to its key name.Key can be used inside square brackets.

Accessing elements from a Dictionary

Accessing element of a nested dictionary:

In order to access the value of any key in nested dictionary, use indexing []

Accessing element of a nested dictionary

Delete Dictionary Elements:

ou can either remove individual dictionary elements or clear the entire contents of a dictionary. You can also delete entire dictionary in a single operation.

To explicitly remove an entire dictionary, just use the del statement. Following is a simple example −

Delete Dictionary Elements

Properties of Dictionary Keys:

Dictionary values have no restrictions. They can be any arbitrary Python object, either standard objects or user-defined objects. However, same is not true for the keys.

There are two important points to remember about dictionary keys −

(a) More than one entry per key not allowed. Which means no duplicate key is allowed. When duplicate keys encountered during assignment, the last assignment wins.

(b)Keys must be immutable. Which means you can use strings, numbers or tuples as dictionary keys but something like [‘key’] is not allowed.

Conclusion:

In this tutorial, you covered the basic properties of the Python dictionary and learned how to access and manipulate dictionary data.

How to Convert a Python String to int

Convert Python String to Int:

To convert a string to integer in Python, use the int() function. This function takes two parameters: the initial string and the optional base to represent the data. In Python an strings can be converted into a integer using the built-in int() function. The int() function takes in any python data type and converts it into a integer.But use of the int() function is not the only way to do so. This type of conversion can also be done using thefloat() keyword, as a float value can be used to compute with integers.

Below is the list of possible ways to convert an integer to string in python:

1. Using int() function:

Syntaxint(string)

Example:

Using int() function

Output:

Using int() function output
As a side note, to convert to float, we can use float() in python:

Example:

use float() in python

Output:

use float() in python output
2. Using float() function:

We first convert to float, then convert float to integer. Obviously the above method is better (directly convert to integer).

Syntax: float(string)

Example:

Using-float-function

Output:

Using float() function output

If you have a decimal integer represented as a string and you want to convert the Python string to an int, then you just follow the above method (pass the string to int()), which returns a decimal integer.But By default, int() assumes that the string argument represents a decimal integer. If, however, you pass a hexadecimal string to int(), then you’ll see a ValueError

For value error

The error message says that the string is not a valid decimal integer.

When you pass a string to int(), you can specify the number system that you’re using to represent the integer. The way to specify the number system is to use base:

Now, int() understands you are passing a hexadecimal string and expecting a decimal integer.

Conclusion:

This article is all about how to convert python string to int.All methods are clearly explained here. Now I hope you’re comfortable with the ins and outs of converting a Python string to an int.

Convert integer to string in Python

We can convert an integer data type using the python built-in str() function. This function takes any data type as an argument and converts it into a string. But we can also do it using the “%s” literal and using the .format() function.

How to convert an integer to a string in Python

Below is the list of possible ways to convert an integer to string in python:

1. Using str() function :

Syntax: str(integer_value)

Convert Integer to String in Python Using str() function
Output:
Convert Integer to String in Python Using str() function Output

2. Using “%s” keyword:

Syntax: “%s” % integer

Convert Integer to String in Python Using s keyword

Output:

Convert Integer to String in Python Using str() function Output
3. Using .format() function:

Syntax: ‘{}’.format(integer)

Convert Integer to String in Python Using format function
Output:

Using .format() function op

4. Using f-string:

Syntax: f'{integer}’

Convert-Integer-to-String-in-Python-Using-f-string
Output:

Convert Integer to String in Python Using f string output

Conclusion:

We have defined all methods of converting the integer data type to the string type. You can use one of them according to your requirement.

Python – Ways to remove duplicates from list

List is an important container and used almost in every code of day-day programming as well as web-development, more it is used, more is the requirement to master it and hence knowledge of its operations is necessary. This article focuses on one of the operations of getting the unique list from a list that contains a possible duplicated. Remove duplicates from list operation has large number of applications and hence, its knowledge is good to have.

How to Remove Duplicates From a Python List

Method 1 : Naive method

In Naive method, we simply traverse the list and append the first occurrence of the element in new list and ignore all the other occurrences of that particular element.

# Using Naive methods:

Using Naive method

Output :

Remove duplicates from list using Naive method output

Method 2 : Using list comprehension

List comprehensions are Python functions that are used for creating new sequences (such as lists, tuple, etc.) using previously created sequence. This makes code more efficient and easy to understand. This method has working similar to the above method, but this is just a one-liner shorthand of longer method done with the help of list comprehension.

# Using list comprehension

Remove duplicates from list using list comprehension
Output :

Remove duplicates from list using list comprehension output

Method 3 : Using set():

We can remove duplicates from a list using an inbuilt function called set(). The set() always return distinct elements. Therefore, we use the set() for removing duplicates.But the main and notable drawback of this approach is that the ordering of the element is lost in this particular method.

# Using set()

Remove duplicates from list using set method
Output :

Remove duplicates from list using set method output

Method 4 : Using list comprehension + enumerate():

Enumerate can also be used for removing duplicates when used with the list comprehension.It basically looks for already occurred elements and skips adding them. It preserves the list ordering.

# Using list comprehension + enumerate()

Using list comprehension + enumerate()
Output :

Using list comprehension + enumerate() output
Method 5 : Using collections.OrderedDict.fromkeys():

This is fastest method to achieve the particular task. It first removes the duplicates and returns a dictionary which has to be converted to list. This works well in case of strings also.

# Using collections.OrderedDict.fromkeys()

Using collections.OrderedDict.fromkeys()
Output :

Using collections.OrderedDict.fromkeys() output

Conclusion :

In conclusion, nowyou may know “how to remove duplicates from a list in python?“. There are different ways but the using collections.OrderedDict.fromkeys() method is the best in accordance with the programming efficiency of the computer.