Dive into Daunting Lists and Dictionaries in Python
Tags: beginners, programming, tutorial, python
Published: 2022-09-01 02:46:30

As I promised, here I am! I have come again with an in-depth blog post for Python lists and dictionaries. In this blog, we will take a look at the in-built methods for lists and dictionaries provided by python. There are not many complex methods that exist in python. All the in-built methods are very intuitive from name only. So, let's get started!

![Get Started with Lists and Dictionary in Python](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/aznmj1yh8ia08u1uvnid.png)

# Lovely Lists Data Type in Python

Python provides several in-built methods with the list. Some of them, you will use on a day-to-day basis but some you might never use. So, let's focus on important ones.

1. insert(), append() & extend()
2. remove(), pop(), del & clear()
3. count(), index() & len()
4. sort() & reverse()
5. copy()

## insert(), append() & extend()

### insert()

Syntax: `list.insert(position, element)`
Insert() method adds an element at the specified position in the list. The element can be any of the in-built data types.

1). Insert string into the list

```python
list1 = ["Python", "Programming"]
str1 = "Learn"
list2 = ["From", "Sahil Fruitwala"]

list1.insert(0, str1)
list1.insert(3, list2)

print(list1)

#OUTPUT: ['Learn', 'Python', 'Programming', ['From', 'Sahil Fruitwala']]

```

2). Insert number and boolean into the list

```python
list1 = ["Python", "Programming"]
number1 = 13
boolean1 = False

list1.insert(0, number1)
list1.insert(10, boolean1)

print(list1)

# OUTPUT: ['Python', 'Programming', 13, False]

```

Here, if we add any number more than the ending index data will be added at the end of the list. So, when we did `list1.insert(10, boolean1)`, as the list doesn't have ten elements or the 10th index, it will add boolean data at the end of the list.

### append()

Syntax: `list.append(element)`
The append method adds an element at the end of the list. We can use any data type with the append method as well.

```python
list1 = ["Python", "Programming"]
str1 = "Learn"
list2 = ["From", "Sahil Fruitwala"]

list1.append(str1)
list1.append(list2)

print(list1)
# OUTPUT: ['Python', 'Programming', 'Learn', ['From', 'Sahil Fruitwala']]

```

### extend()

Syntax: `list.extend(iterable_element)`
Extend method adds every element of iterable/sequence (string, list, tuple, set) data type at the end of the list.

```python
list1 = ["Python", "Programming"]
str1 = "Learn"
list2 = ["From", "Sahil Fruitwala"]
tuple1 = ("in", "Python 101")
set1 = {"The", "Blog Series"}

list1.extend(str1)
list1.extend(list2)
list1.extend(tuple1)
list1.extend(set1)

print(list1)

# OUTPUT: ['Python', 'Programming', 'L', 'e', 'a', 'r', 'n', 'From', 'Sahil Fruitwala', 'in', 'Python 101', 'The', 'Blog Series']

```

## remove(), pop(), del & clear()

### remove()

Syntax: `list.remove(element)`
The remove method removes the first instance of a specific element from the list.

```python
list1 = [ 1, 2, 1, 1, 4, 5 ]
list1.remove(1)
print(list1)

# OUTPUT: [2, 1, 1, 4, 5]

```

If we try to remove the element that does not exist in the list, then python will throw the error.

```python
list1 = [ 1, 2, 1, 1, 4, 5 ]
list1.remove(6)
print(list1)

'''
OUTPUT:

Traceback (most recent call last):
  File "C:\\Users\\Sahil\\Desktop\\1.py", line 2, in <module>
    list1.remove(6)
ValueError: list.remove(x): x not in list

'''

```

### pop()

Syntax: `list.pop()` or `list.pop(index)`
The pop method by default removes the last element of the list and returns it. We can also pass the specific index to the pop method.

```python
list1 = ["Python", "C++", "Java", "PHP", "Rust"]
pop_element = list1.pop()
print(pop_element)
print(list1)

# OUTPUT: Rust
# OUTPUT: ['Python', 'C++', 'Java', 'PHP']

pop_element = list1.pop(1)
print(pop_element)
print(list1)

# OUTPUT: C++
# OUTPUT: ['Python', 'Java', 'PHP']

```

### del

Syntax: `del list[index]`
The keyword **del** removes elements from the specific index in the list. If we use the `del` keyword without any index, it will remove the complete variable from the computer's memory.

```python
list1 = ["Python", "C++", "Java", "PHP", "Rust"]
del list1[2]
print(list1)

# OUTPUT: ['Python', 'C++', 'PHP', 'Rust']

list1 = ["Python", "C++", "Java", "PHP", "Rust"]
del list1

```

### clear()

Syntax: `list.clear()`
The Clear method removes all elements from the list.

```python
list1 = ["Python", "C++", "Java", "PHP", "Rust"]
list1.clear()
print(list1)

# OUTPUT: []

```

## count(), index() & len()

### count()

Syntax: `list.count(element)`
The count method returns the number of occurrences of a specific element in a list.

```python
fruits = ['apple', 'banana', 'cherry', 'mango', 'grape', 'cherry', 'cherry']
num_of_cherry = fruits.count("cherry")
print(num_of_cherry)

# OUTPUT: 3

```

### index()

Syntax: `list.index(element)`
The index method returns the index of a specific element in the list.

```python
fruits = ['apple', 'banana', 'cherry', 'mango', 'grape', 'cherry', 'cherry']
index_of_cherry = fruits.index("cherry")

print(index_of_cherry)

# OUTPUT: 2

```

Note: If an element does not exist ion list index() will throw the error.

### len()

Syntax: `len(list)`
Len method returns the length of any sequence datatype and dictionary.

```python
list1 = ['apple', 'banana', 'cherry', 'mango', 'grape', 'cherry', 'cherry']
str1 = "Python Programming"
dict1 = {'lang':"Python", 'Year':2021}

print(len(list1))
print(len(str1))
print(len(dict1))

# OUTPUT: 7
# OUTPUT: 18
# OUTPUT: 2

```

## sort() & reverse()

### sort()

Syntax: `list.sort()`
The sort method sorts all the elements of the list by default into ascending order. We can do the sort operation in descending order by providing the **reverse=True** argument in the sort function.

```python
nums = [2, 5, 1, 7, 2, 3, 4, 5, 6]

nums.sort()
print(nums)
# OUTPUT: [1, 2, 2, 3, 4, 5, 5, 6, 7]

nums.sort(reverse=True)
print(nums)
# OUTPUT: [7, 6, 5, 5, 4, 3, 2, 2, 1]

```

The sort method is an in-place method. It means, it does not return any value and does all the operations internally. That is the reason why we have not assigned `nums.sort()` to any other value. If we do that we will get the following result.

```python
nums = [2, 5, 1, 7, 2, 3, 4, 5, 6]

new_nums = nums.sort()
print(new_nums)

# OUTPUT: None

```

### reverse()

Syntax: `list.reverse()`
As the name suggests, the reverse method reverses the whole list. The reverse method is also an in-place method.

```python
nums = [2, 5, 1, 7, 2, 3, 4, 5, 6]

nums.reverse()
print(nums)
# OUTPUT: [6, 5, 4, 3, 2, 7, 1, 5, 2]

```

## copy()

Syntax: `list.copy()`

There will occur many cases during development when we want to copy the list. The copy method helps us to do that.

```python
num1 = [2, 5, 1, 7, 2, 3, 4, 5, 6]
num2 = num1

num2.reverse()
print(num1)
print(num2)

# OUTPUT:
[6, 5, 4, 3, 2, 7, 1, 5, 2]
[6, 5, 4, 3, 2, 7, 1, 5, 2]

```

In the general case, **num2** will have copied data of **num1**. But, in the case of the list, it just copies the memory address of num1 to num2. So, whatever changes we make in num2 they all will reflect in num1, and vice versa. So, to copy lists properly we have to use the copy method.

```python
num1 = [2, 5, 1, 7, 2, 3, 4, 5, 6]
num2 = num1.copy()

num2.reverse()
print(num1)
print(num2)

# OUTPUT:
[2, 5, 1, 7, 2, 3, 4, 5, 6]
[6, 5, 4, 3, 2, 7, 1, 5, 2]

```

Alternatively, you can use the `list(list_name)` as well.

```python
num1 = [2, 5, 1, 7, 2, 3, 4, 5, 6]
num2 = list(num1)

num2.reverse()
print(num1)
print(num2)

# OUTPUT:
[2, 5, 1, 7, 2, 3, 4, 5, 6]
[6, 5, 4, 3, 2, 7, 1, 5, 2]

```

# Dope Dictionary Data Type in Python

1. clear(), pop() & popitem()
2. get(), items() & keys()
3. update() & fromkeys()

## clear(), pop() & popitem()

### clear()

Syntax: `dictionary.clear()`
The clear() method for the dictionary works the same way it works in the list. This method removes all the elements from a dictionary.

```python
blog =	{
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

print(blog)
# OUTPUT: {'language': 'Python', 'Blogger': 'Sahil Fruitwala', 'year': 2021}

blog.clear()
print(blog)
# OUTPUT: {}

```

### pop()

Syntax: `dictionary.pop()` or `dictionary.pop(key, default_value)`
The pop() method removes and returns the specific element from the dictionary.

```python
blog =	{
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

print(blog)
# OUTPUT: {'language': 'Python', 'Blogger': 'Sahil Fruitwala', 'year': 2021}

year = blog.pop("year")
print(blog) # OUTPUT: {'language': 'Python', 'Blogger': 'Sahil Fruitwala'}
print(year) # 2021

```

The pop() is used when we want some default value in case the key does not exist.

```python
blog =	{
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

year = blog.pop("years", "NotFound")
print(blog) # OUTPUT: {'language': 'Python', 'Blogger': 'Sahil Fruitwala', 'year': 2021}

print(year) # NotFound

```

### popitem()

Syntax: `dictionary.popitem()`
The popitem() removes the last key-value pair from the dictionary and returns as a tuple.

```python
blog =  {
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

year = blog.popitem()
print(blog)
# OUTPUT: {'language': 'Python', 'Blogger': 'Sahil Fruitwala'}

print(year)
# OUTPUT: ('year', 2021)

```

## get(), items(), keys() & values()

### get()

Syntax: `dictionary.get(keyname)`
The get method extracts the value of the specified key

```python
blog =  {
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

year = blog.get("year")
print(year)
# OUTPUT: 2021

```

### items()

Syntax: `dictionary.items()`
The items method returns the view object of the dictionary. The view object contains all the key-value pairs. One drawback of using the items() method is, that if you make any change in the root or original dictionary it will reflect in the view object variable as well.

```python
blog =  {
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

view_object = blog.items()

blog['year'] = 2022
print(view_object)

# OUTPUT: dict_items([('language', 'Python'), ('Blogger', 'Sahil Fruitwala'), ('year', 2022)])

```

### keys() & values()

Syntax: `dictionary.keys()` and `dictionary.values()`
As the name suggests, keys() and values() methods return the **view object** or keys and values of a given dictionary.

```python
blog =  {
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

keys = blog.keys()
print(keys)
# OUTPUT: dict_keys(['language', 'Blogger', 'year'])

values = blog.values()
print(values)
# OUTPUT: dict_values(['Python', 'Sahil Fruitwala', '2022'])

```

## update() & fromkeys()

### update()

Syntax: `dictionary.get({key:value})`
The update method updates the existing key with a specified value and if the key does not exist it adds the new key-value pair.

```python
blog =  {
  "language": "Python",
  "Blogger": "Sahil Fruitwala",
  "year": 2021
}

blog.update({"type": "New"})
print(blog)
# OUTPUT: {'language': 'Python', 'Blogger': 'Sahil Fruitwala', 'year': 2021, 'type': 'New'}

blog.update({"type": "OLD"})
print(blog)
# OUTPUT: {'language': 'Python', 'Blogger': 'Sahil Fruitwala', 'year': 2021, 'type': 'OLD'}

```

### fromkeys()

Syntax: `dict.fromkeys(keys, defaultvalue)`
When we new parameters from the beginning but are not aware of their values to them, at that time we can create a dictionary with **keys** and default **values**.

```Python
keys =  ( "Python", "Sahil Fruitwala", 2021 )

blog = dict.fromkeys(keys)
print(blog)
# OUTPUT: {'Python': None, 'Sahil Fruitwala': None, 2021: None}

blog1 = dict.fromkeys(keys, "")
print(blog1)
# OUTPUT: {'Python': '', 'Sahil Fruitwala': '', 2021: ''}

```

---

# Conclusion

Finally! We are at the end of this section 😁.

I know, it is a lot to take in at a time. But, you don't need to remember everything that I have mentioned here. I just showed you so that you can recall what is possible and what is not. There are some other methods as well that I have not mentioned here.

If you want to find out more about the List and Dictionary methods, check out [GeeksforGeeks](https://www.geeksforgeeks.org/python-dictionary-methods/).

---

That was it!

Make sure to share any thoughts, questions, or concerns. Let me know if you need any help or want to discuss something. Reach out to me on [Twitter](https://twitter.com/sahil_fruitwala) or [LinkedIn](https://www.linkedin.com/in/sahilfruitwala/). Make sure to share any thoughts, questions, or concerns. I would love to see them.

Thank you for your precious time ❤

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