What is __init__ in Python?

👉Equivalent to constructors in OOP terminology, __init__ is a reserved method in Python classes. The __init__ method is called automatically whenever a new object is initiated. This method allocates memory to the new object as soon as it is created. This method can also be used to initialize variables.

Syntax

class Human:
# init method or constructor
def __init__(self, age):
self.age = age
# Sample Method
def say(self):
print('Hello, my age is', self.age)
h= Human(22)
h.say()

Output:

Hello, my age is 22

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What are the common built-in data types in Python?

Python supports the below-mentioned built-in data types:

Immutable data types:

👉Number
👉String
👉Tuple

Mutable data types:

👉List
👉Dictionary
👉set

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Explain split(), sub(), subn() methods of “re” module in Python?

These methods belong to the Python RegEx or ‘re’ module and are used to modify strings.

👉split(): This method is used to split a given string into a list.

👉sub(): This method is used to find a substring where a regex pattern matches, and then it replaces the matched substring with a different string.

👉subn(): This method is similar to the sub() method, but it returns the new string, along with the number of replacements.

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What is a map function in Python?

The map() function in Python has two parameters, function and iterable. The map() function takes a function as an argument and then applies that function to all the elements of an iterable, passed to it as another argument. It returns an object list of results.

Example:

def calculateSq(n):
return n*n
numbers = (2, 3, 4, 5)
result = map( calculateSq, numbers)
print(result)

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Explain all file processing modes supported in Python?

Python has various file processing modes.

For opening files, there are three modes:

👉read-only mode (r)
👉write-only mode (w)
👉read–write mode (rw)

For opening a text file using the above modes, we will have to append ‘t’ with them as follows:

👉read-only mode (rt)
👉write-only mode (wt)
👉read–write mode (rwt)

Similarly, a binary file can be opened by appending ‘b’ with them as follows:

👉read-only mode (rb)
👉write-only mode (wb)
👉read–write mode (rwb)

To append the content in the files, we can use the append mode (a):

For text files, the mode would be ‘at’
For binary files, it would be ‘ab’

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What is the lambda function in Python?

A lambda function is an anonymous function (a function that does not have a name) in Python. To define anonymous functions, we use the ‘lambda’ keyword instead of the ‘def’ keyword, hence the name ‘lambda function’. Lambda functions can have any number of arguments but only one statement.

Example:

l = lambda x,y : x*y
print(a(5, 6))

Output:30

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What is self in Python?

Self is an object or an instance of a class. This is explicitly included as the first parameter in Python. On the other hand, in Java it is optional. It helps differentiate between the methods and attributes of a class with local variables.

The self variable in the init method refers to the newly created object, while in other methods, it refers to the object whose method was called.

Syntax:

Class A:
def func(self):
print(“Hi”)

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What is the difference between append() and extend() methods?

Both append() and extend() methods are methods used to add elements at the end of a list.

👉append(element): Adds the given element at the end of the list that called this append() method

👉extend(another-list): Adds the elements of another list at the end of the list that called this extend() method

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How is Multithreading achieved in Python?

👉Python has a multi-threading package ,but commonly not considered as good practice to use it as it will result in increased code execution time.

👉Python has a constructor called the Global Interpreter Lock (GIL). The GIL ensures that only one of your ‘threads’ can execute at one time.The process makes sure that a thread acquires the GIL, does a little work, then passes the GIL onto the next thread.

👉This happens at a very Quick instance of time and that’s why to the human eye it seems like your threads are executing parallely, but in reality they are executing one by one by just taking turns using the same CPU core.

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Inverts a dictionary with non-unique hashable values.

👉Create a collections.defaultdict with list as the default value for each key.

👉Use dictionary.items() in combination with a loop to map the values of the dictionary to keys using dict.append().

👉Use dict() to convert the collections.defaultdict to a regular dictionary.

CODE:

from collections import defaultdict

def collect_dictionary(obj):
inv_obj = defaultdict(list)
for key, value in obj.items():
inv_obj[value].append(key)
return dict(inv_obj)

Example:

ages = {
'Peter': 10,
'Isabel': 10,
'Anna': 9,
}
collect_dictionary(ages)

Output: { 10: ['Peter', 'Isabel'], 9: ['Anna'] }

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Walrus operator:

The Walrus or := operator is one of the latest additions to python 3.8.
It is an assignment operator that lets you assign value to a variable within an expression like conditional statements, loops, etc.


Example

If we want to check and print the length of a list:

Mylist = [1,2,3]
if(l := len(mylist) > 2)
print(l)

Output

3

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What Is FastAPI?

FastAPI is a modern, high-performance web framework for building APIs with Python based on standard type hints.


It has the following key features:

👉Fast to run: It offers very high performance, on par with NodeJS and Go, thanks to Starlette and pydantic.

👉Fast to code: It allows for significant increases in development speed.

👉Reduced number of bugs: It reduces the possibility for human-induced errors.

👉Intuitive: It offers great editor support, with completion everywhere and less time debugging.

👉Straightforward: It’s designed to be uncomplicated to use and learn, so you can spend less time reading documentation.

👉Short: It minimizes code duplication.

👉Robust: It provides production-ready code with automatic interactive documentation.

👉Standards-based: It’s based on the open standards for APIs, OpenAPI and JSON Schema.

You can use this instead of Django and Flask

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Difference between list and tuple in python

🔸List is mutable ( you can modify the original list) and it's values are written in sqare brackets [ ]

🔸Tuple is immutable ( you can't modify it) and it's values are written in parentheses ( ) delimited by comma( , )

🔸To convert list to tuple - we use tuple() function
list1 = [1,2,3]
print(tuple(list1)) Output : (1,2,3)

🔸 For single element list
list1 = [1]
print(tuple(list1)) Output : (1, )

▪️a tuple is a tuple because of comma not because of parentheses


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To shuffle pandas DataFrame df (in a reproducible way):

df = df.sample(frac=1, random_state=123).reset_index(drop=True)

Alternatively, you can use sklearn.utils.shuffle().

#pandas

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Do you know abou .strip()

From the above example you can see that it removed all the characters mentioned in .strip('comw.') and returns the remaining string


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Useful Pandas🐼 method you should definitely know

✅ head()
✅ info()
✅ fillna()
✅ melt()
✅ pivot()
✅ query()
✅ merge()
✅ assign()
✅ groupby()
✅ describe()
✅ sample()
✅ replace()
✅ rename()


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