Questions
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How to leave/exit/deactivate a Python virtualenv?
To leave a Python virtual environment, you can use the deactivate command. This will return you to the system's default Python environment. Here's an example of how you would use deactivate: source...
How to print without a newline or space in Python?
To print without a new line, you need to provide one additional argument end and set its value to something other than the default \n which will break the line. You can set it to an empty character...
How do I uppercase or lowercase a string in Python?
To uppercase a string in Python, you can use the upper() method of the string. For example: string = "hello" uppercasestring = string.upper() print(uppercasestring) # prints "HELLO" To lowercase a...
How do I get a substring of a string in Python?
To get a substring of a string in Python, you can use the string slicing notation, which is string[start:end], where start is the index of the first character of the substring, and end is the index...
How to upgrade all Python packages with pip?
You can use the pip install command with the --upgrade option to upgrade all packages in your Python environment. Here's the basic syntax: pip install --upgrade [package1] [package2] ... To upgrade...
How do I sort a list of dictionaries by a value of the dictionary in Python?
In Python, you can use the sorted() function to sort a list of dictionaries by a specific value of the dictionary. The sorted() function takes two arguments: the list to be sorted, and a key functi...
How do I get the last element of a list in Python?
To get the last element of a list in Python, you can use the negative indexing feature of the list data type. For example: mylist = [1, 2, 3, 4, 5] lastelement = mylist[-1] # lastelement will be 5...
How do I parse a string to a float or int in Python?
To parse a string to a float in Python, you can use the float() function. This function takes a string as input and returns a floating point number constructed from it. For example: float('3.14') #...
How to check if a given key already exists in a dictionary in Python?
You can use the in keyword to check if a key exists in a dictionary. For example: my_dict = {'a': 1, 'b': 2, 'c': 3} if 'a' in my_dict: print("Key 'a' exists in the dictionary") if 'd' in my_di...
How to remove a key from a Python dictionary?
To remove a key from a dictionary, you can use the del statement. Here's an example: my_dict = {'a': 1, 'b': 2, 'c': 3} del my_dict['b'] print(my_dict) # Output: {'a': 1, 'c': 3} Alternatively, yo...
How to find the current directory and file's parent directory in Python?
You can use the os module in Python to find the current directory and the parent directory of a file. To get the current directory, you can use os.getcwd(). To get the parent directory of a file, y...
How to convert string into datetime in Python?
To convert a string into a datetime object in Python, you can use the datetime.strptime() function. This function allows you to specify the format of the input string, and it will return a datetime...
How do I access environment variables in Python?
You can access environment variables in Python using the os module. Here's an example: import os Access an environment variable value = os.environ['VARIABLE_NAME'] Set an environment variable os.en...
How do I split Python list into equally-sized chunks?
To split a list into equally sized chunks, you can use the grouper function from the itertools module. Here's an example of how you can use it: from itertools import zip_longest def grouper(iterabl...
How do I print colored text to the terminal in Python?
You can use ANSI escape codes to print colored text to the terminal in Python. Here is an example of how you can do this: def colored_text(color, text): colors = { "red": "\033[91m", ...
How to manually raising (throwing) an exception in Python?
To manually raise an exception in Python, use the raise statement. Here is an example of how to use it: def calculatepayment(amount, paymenttype): if paymenttype != "Visa" and paymenttype != "M...
How do I make function decorators and chain them together in Python?
In Python, a decorator is a design pattern to extend the functionality of a function without modifying its code. You can create a decorator function using the @decorator_function syntax, or by call...
Understanding Python super() with init() methods
The super() function is used to call a method from a parent class. When used with the __init__ method, it allows you to initialize the attributes of the parent class, in addition to any attributes ...
How do I delete a file or folder in Python?
You can use the os module to delete a file or folder in Python. To delete a file, you can use the os.remove() function. This function takes the file path as an argument and deletes the file at that...
What is the difference between Python's list methods append and extend?
The append() method adds an item to the end of the list. The item can be of any type, and you can use the method to add multiple items by separating them with a comma. For example: fruits = ['apple...
How do I make a time delay in Python?
There are a few ways to make a time delay in Python. Here are three options: time.sleep(): You can use the sleep() function from the time module to add a delay to your program. The sleep() function...
How do I pass a variable by reference in Python?
In Python, variables are passed to functions by reference. This means that when you pass a variable to a function, you are passing a reference to the memory location where the value of the variable...
What does ** and * do for parameters in Python?
In Python, the * symbol is used to indicate that an argument can be passed to a function as a tuple. The ``** symbol is used to indicate that an argument can be passed to a function as a dictionary...
How do I check if a list is empty in Python?
You can check if a list is empty by using the len() function to check the length of the list. If the length of the list is 0, then it is empty. Here's an example: my_list = [] if len(my_list) == 0:...
How do I concatenate two lists in Python?
You can concatenate two lists in Python by using the + operator or the extend() method. Here is an example using the + operator: list1 = [1, 2, 3] list2 = [4, 5, 6] list3 = list1 + list2 print(list...
How can I add new keys to Python dictionary?
You can add a new key-value pair to a dictionary in Python by using the square brackets [] to access the key you want to add and then assigning it a value using the assignment operator =. For examp...
What is init.py for?
In Python, the __init__.py file is used to mark a directory as a Python package. It is used to initialize the package when it is imported. The __init__.py file can contain code that will be execute...
How do I sort a dictionary by key or value?
To sort a dictionary by key in Python, you can use the sorted function, like this: d = {"a": 1, "b": 2, "c": 3} sorted_d = sorted(d.items(), key=lambda x: x[0]) sorted_d will now be a list of tuple...
How do I list all files in a directory using Python?
To list all files in a directory in Python, you can use the os module and its listdir() function. This function returns a list of all the files and directories in the specified directory. Here's an...
How to Copy Files in Python?
To copy a file in Python, you can use the shutil module. Here is an example of how you can use the shutil.copy() function to copy a file: import shutil shutil.copy('/path/to/source/file', '/path/to...
Convert bytes to a string in Python and vice versa?
To convert a string to bytes in Python, you can use the bytes function. This function takes two arguments: the string to encode and the encoding to use. The default encoding is utf-8. Here is an ex...
What is the difference between str and repr in Python?
In Python, str is used to represent a string in a more readable format, while repr is used to represent a string in an unambiguous and official format. The main difference between the two is that s...
How to check if a string contains a substring in Python?
There are multiple ways to check if a string contains a specific substring. Using in keyword You can use in keyword to check if a string contains a specific substring. The expression will return bo...
How to catch multiple exceptions in one line (except block)?
To catch multiple exceptions in one except block, you can use the following syntax: except (SomeException, DifferentException) as e: pass # handle the exception or pass If you are using Pyt...
How do I get the current time in Python?
There are two ways you can get the current time in python. using the datetime object using the time module Using the datetime object First, you need to import the datetime module. Then by calling t...
How to iterate over Python dictionaries using 'for' loops?
Let’s assume the following dictionary: my_dictionary = { 'key1': 'value1', 'key2': 'value2', 'key3': 'value3' } There are three main ways you can iterate over the dictionary. Iterate ov...
Finding the Index of an Item in a Python List?
To find an index of the first occurrence of an element in a given list, you can use index method of List class with the element passed as an argument. The syntax is the following: my_list = [1...
Understanding slicing in Python?
Slicing is a way of extracting a specific part of an array. The syntax is following: mylist[start:end] # items start through end-1 mylist[start:] # items start through the rest of the array ...
Difference between static and class methods in Python?
Class method To create a class method, use the @classmethod decorator. Class methods receive the class as an implicit first argument, just like an instance method receives the instance. The class m...
How to flatten a list in Python?
You can flatten a list in python using the following one-liner: flat_list = [item for sublist in l for item in sublist] In the example above, l is the list of lists that is to be flattened. The pre...
How to access the index in for loops in Python?
In python, if you are enumerating over a list using the for loop, you can access the index of the current value by using enumerate function. my_list = [1,2,3,4,5,6,7,8,9,10] for index, value in enu...
How can I safely create a nested directory in Python?
The most common way to safely create a nested directory in Python is using the pathlib or os modules. Using pathlib You can create a nested directory in python 3.5 or later using the Path and mkdir...
How Execute a Program or Call a System Command in Python?
In Python, you can execute a system command using the os.system. However, subprocess.run is a much better alternative. The official also documentation recommends subprocess.run over the os.system. ...
How do I merge two dictionaries in a single expression in Python?
To merge two dictionaries in a single expression you can use the dictionary unpacking operator **. This creates a new dictionary and unpacks all key-value pairs into the new dictionary. Let’s look ...
How do I check whether a file exists without exceptions?
There are two ways you can safely check if a file exists at a given path. Using the os.path You can use the exists function from the os.path package to check if a file exists at the given path. fro...
What are metaclasses in Python?
In Python, a metaclass is the class of a class. It defines how a class behaves, including how it is created and how it manages its instances. A metaclass is defined by inheriting from the built-in ...
How to use the ternary conditional operator in Python?
The ternary conditional operator is a shortcut when writing simple conditional statements. If the condition is short and both true and false branches are short too, there is no need to use a multi-...
What Does if name == “main”: Do in Python?
The if __name__ == "main" is a guarding block that is used to contain the code that should only run went the file in which this block is defined is run as a script. What it means is that if you run...
What Does the “yield” Keyword Do in Python?
To better understand what yield does, you need first to understand what generator and iterable are. What is iterable When you use a list or list-like structure, you can read the values from the lis...
Where can I find MySQL logs in phpMyAdmin?
In the older version of the phpMyAdmin control panel, there is Binary log in which all logs are stored. This can be opened by clicking Status → Binary log In newer versions, the Status page looks l...
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