what happens to an if statement if you dont declare an else

An if else Python argument evaluates whether an expressio n is tr ue or false. If a conditio n is tr ue, the "if" argument executes. Otherwise, the "else" argument executes. Python if else statements aid coders control the flow of their programs.

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When you lot're writing a program, you may want a block of code to run only when a certain condition is met. That'due south where conditional statements come in. Conditional statements permit you to control the catamenia of your program more effectively.

In Python, the if and if…else statements are used to perform conditional operations. This tutorial will discuss, with reference to examples, the basics of the if, if…else, and elif statements in Python. We'll also discuss how to use nested if statements.

Python if Statement

A Python if statement evaluates whether a status is equal to truthful or false. The statement will execute a block of lawmaking if a specified status is equal to true. Otherwise, the block of code within the if argument is not executed.

Let's write a program that prints the price of a sandwich order. The price of a sandwich order should only be displayed if the client has ordered a ham gyre. Our sandwich social club is a Python cord. Here'due south the code for our plan:

sandwich_order = "Ham Ringlet"  if sandwich_order == "Ham Roll": 	print("Price: $1.75")

Our code returns: Price: $1.75

We have declared a variable called sandwich_order. This variable has been assigned the value Ham Coil.

We use an if statement to check whether sandwich_order is equal to Ham Roll. If our condition is true, our print() statement is exist executed. If our condition is false, nada will happen.

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Our sandwich_order variable is equal to Ham Ringlet. This ways that our if statement is executed. At present, let's see what happens when we modify our sandwich order to Cheese Roll:

sandwich_order = "Cheese Roll"  if sandwich_order == "Ham Roll": 	print("Price: $i.75")

Our code returns nothing. The print() statement in our code is not given the chance to execute. This is considering our sandwich order is non equal to Ham Roll.

if else Python Statement

An if…else Python statement checks whether a status is true. If a condition is true, the if statement executes. Otherwise, the else argument executes.

So far, we have used an if argument to exam for whether a item condition is met. Simply, what if we want to do something if a condition is non met?

Suppose we are edifice an app that checks whether a customer at a local restaurant has run upwardly a tab. If the customer has run up a tab over $xx, they need to pay it off before they can social club more food. Nothing should happen if the customer does not have a tab accrued over $20.

To accomplish this job, we could use the post-obit lawmaking:

tab = 29.95  if tab > 20: 	print("This user has a tab over $20 that needs to be paid.") else: 	print("This user's tab is below $20 that does not require firsthand payment.")

Our code returns: This user has a tab over $20 that needs to be paid.

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Permit'southward walk through how our code works. Starting time, we declare a Python variable called tab. This variable tracks a customer's tab. We use an if argument to check whether the customer's tab is greater than 20.

If a customer's tab is worth more than $20, the impress() argument afterwards our if statement is executed. Otherwise, the print() statement after our Python if…else clause is executed.

Because our customer'southward tab is over $20, the Python interpreter executes our if statement. This instructs our program to print a message to the console. The message tells united states that the customer must pay their tab.

Allow's set the customer's tab to $0 and encounter what happens:

This user's tab is beneath $twenty which does non crave immediate payment.

Our code returns a unlike output. The customer's tab is non over $20. This means the contents of our else statement are executed instead of our if statement.

Python elif Statement

A Python elif argument checks for some other condition if all preceding conditions are not met. They announced later on a Python if statement and earlier an else statement. You can use as many elif statements as you desire.

In our to a higher place example, we created a conditional argument with two possible outcomes. If the user's tab was over $20, a bulletin was printed to the console. If a user's tab was under $20, a dissimilar bulletin was printed to the panel.

In some cases, we may want to evaluate multiple conditions and create outcomes for each of those conditions. That's where the elif condition comes in.

elif Python Argument Case

Let'south return to our sandwich example from before. Suppose we want to have 4 potential outputs from our program, depending on the sandwich filling a customer chooses. These are:

• Ham Roll: $1.75
• Cheese Ringlet: $ane.80
• Bacon Roll: $2.x
• Other Filled Ringlet: $two.00

We could employ the following lawmaking to summate the cost of the client's society:

sandwich_order = "Bacon Ringlet"  if sandwich_order == "Ham Roll": 	print("Price: $1.75") elif sandwich_order == "Cheese Roll": 	impress("Price: $one.80") elif sandwich_order == "Bacon Gyre": 	print("Price: $2.10") else: 	print("Toll: $two.00")

Our code returns: Cost: $2.x.

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Our code has four possible outcomes:

• If a client orders a ham roll, the contents of the "if" statement are executed. This prints "Price: $1.75" to the panel.
• If a customer orders a cheese whorl, the contents of the first "elif" statement are executed. This prints "Cost: $1.80" to the console.
• If a customer orders a bacon roll, the contents of the 2d "elif" statement are run. This prints "Price: $ii.ten" to the panel.
• We display "Price: $ii.10" on the panel if a customer orders a curl with a different filling.

We used an if argument to test for a specific condition. Our two elif blocks to test for alternative conditions. The else statement returns a value in case no conditions are met.

We could add together in more elif statements to our in a higher place code if nosotros wanted. If nosotros introduced a new Tuna Roll to our sandwich menu, we could add in a new elif statement. This new statement could print the price of the new card item to the console.

Python Nested if Statements

A nested if argument is an if statement inside another if statement. Nested if statements let you lot check if a condition is met afterward another status has already been met.

Permit'southward return to our sandwich example from earlier. Suppose nosotros want to check whether a customer has ordered a roll that is on our menu. We want to do this earlier we check the prices of the client's order.

Python Nested if Statement Example

A message should be printed to the screen with our default price for non-menu items if a customer has ordered another custom sandwich. Custom sandwiches are sandwiches that are not on our carte (such as a buttered roll, or a jam coil).

However, if a customer has ordered a sandwich that is on our card, nosotros should then bank check to run into the price of that sandwich. We could do and so using this code:

sandwich_order = "Other Filled Roll"  if sandwich_order != "Other Filled Roll":  	if sandwich_order == "Ham Roll": 	print("Toll: $1.75") if sandwich_order == "Cheese Gyre": 	print("Price: $ane.80") elif sandwich_order == "Bacon Roll": 	impress("Toll: $2.10")  else: 	print("Price: $2.00")

Our code returns: Price: $two.00.

First, our program evaluates whether our sandwich order is not equal to Other Filled Curl. Our program will compare the sandwich nosotros have ordered with the list of sandwiches on our menu. This happens if we have ordered a sandwich on the menu.

If we accept ordered a filled coil that is not on our card, the contents of the else argument in our lawmaking are executed.

In this instance, we have ordered a filled roll that is non on our carte du jour. This means that the statement if sandwich_order != Other Filled Roll evaluates to False, so the code in our if statement is executed.

Now, suppose we ordered a ham roll instead. This would cause our first if statement to evaluate to true. This is because Ham Coil is non equal to Other Filled Roll. Our gild volition be compared to the listing of sandwich prices we take specified.

View the Repl.it from this tutorial:

Conclusion

The if else argument lets you control the flow of your programs. First, Python evaluates if a condition is true. If a status is non true and an elif statement exists, another condition is evaluated.

If no conditions are met and an else statement is specified, the contents of an else statement are run. Past using a conditional statement, yous can instruct a programme to only execute a block of code when a condition is met.

Now y'all're ready to start using these statements in your ain code, like a Python proficient! To learn more about coding in Python, read our consummate guide on How to Lawmaking in Python.

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