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Here are some of the most common python programming mistakes/gotchas that programmers commit:Scope name lookups: Python follows scoping rules in order of LEGB(Local, Enclosing, Global, Built-in). Since python has no strict type binding, programmers can reassociate an outer scope variable to another value that might be used in the outer scope later but is now replaced by some other value.Not differentiating between is and =: The is an operator in python checks if both objects refer to the same memory address. The == operator executes __eq__ function which might check for equality differently for different classes.Modifying a list while iterating ... Read More
Here are some of the most common python programming mistakes/gotchas that programmers commit −Scope name lookups − Python follows scoping rules in order of LEGB(Local, Enclosing, Global, Built-in). Since python has no strict type binding, programmers can reassociate an outer scope variable to another value that might be used in the outer scope later but is now replaced by some other value.Not differentiating between is and == − The is an operator in python checks if both objects refer to the same memory address. The == operator executes __eq__ function which might check for equality differently for different classes.Modifying a ... Read More
You can compare 2 variables in an if statement using the == operator. examplea = 10 b = 15 if a == b: print("Equal") else: print("Not equal")OutputThis will give the output −Not EqualYou can also use the is the operator. examplea = "Hello" b = a if a is b: print("Equal") else: print("Not equal")OutputThis will give the output −EqualNote that is will return True if two variables point to the same object, == if the objects referred to by the variables are equal.
There are many ways you can style multiple if conditions. You don't need to use 4 spaces on your second conditional line. So you can use something like &minusl;if (cond1 == 'val1' and cond2 == 'val2' and cond3 == 'val3' and cond4 == 'val4'):# Actual codeYou can also start the conditions from the next line −if ( cond1 == 'val1' and cond2 == 'val2' and cond3 == 'val3' and cond4 == 'val4' ):# Actual codeOr you can provide enough space between if and ( to accomodate the conditions in the same vertical column.if (cond1 == 'val1' ... Read More
The ternary operator cannot be overloaded. Though you can wrap it up in a lambda/function and use it. For exampleresult = lambda x: 1 if x < 3 else 10 print(result(2)) print(result(1000))OutputThis will give the output −1 10
If you want to convert a statement like −if : to a single line, You can use the single line if syntax to do so −if : Another way to do this is leveraging the short-circuiting and operator like − and If is false, then short-circuiting will kick in and the right-hand side won't be evaluated. If is true, then the right-hand side will be evaluated and will be evaluated.
Suppose we have an array arr of positive integers, consider all binary trees such that −Each node has either 0 or 2 children;The values of arr array correspond to the values of each leaf in an inorder traversal of the tree.The value of each non-leaf node is equal to the product of the largest leaf value in its left and right subtree respectively.Among all possible binary trees considered, we have to find the smallest possible sum of the values of each non-leaf node. So if the input arr is [6, 2, 4], then the output will be 32, as there ... Read More
If you want to get an inversion of only first 16 bits of a number, you can take a xor of that number with 65535(16 1s in binary). examplea = 3 # 11 in binary b = a ^ 65535 print(bin(b))OutputThis will give the output −0b1111111111111100
JShell is a command-line tool that allows us to enter Java statements (simple statements, compound statements, or even full methods and classes), evaluates it and prints the result.Forward references are commands that refer to methods, variables, or classes that don't exist in any code we have typed in JShell. As code entered and evaluated sequentially in JShell, these forward references have temporarily unresolved. JShell supports forward references in method bodies, return types, parameter types, variable types, and within a class.In the below code snippet, created a method forwardReference() in Jshell. This method can't be invoked until the variable is declared. If we are trying to attempt to call this method, it throws a ... Read More
You can do Python operator overloading with multiple operands just like you would do it for binary operators. For example, if you want to overload the + operator for a class, you'd do the following −Exampleclass Complex(object): def __init__(self, real, imag): self.real = real self.imag = imag def __add__(self, other): real = self.real + other.real imag = self.imag + other.imag return Complex(real, imag) def display(self): print(str(self.real) + " + " + str(self.imag) + "i") a = Complex(10, 5) b = Complex(5, 10) c = Complex(2, 2) d = a + b + c d.display()OutputThis will give the output −17 + 17i