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Python Python Basics Types and Branching If, Else and Elif

Posted by Jamshaid Ali
Jamshaid Ali
189 Points

Can someone explain this a little more i didnt quite understand it

Can someone please explain the video a little more and how the colons and equal equal signs work.

Can you also elaborate more on the if and else and elif a bit more to please.

3 Answers

Megan Amendola
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Megan Amendola
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Megan Amendola
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Megan Amendola
Treehouse Teacher

Hi! Conditionals are pieces of code that run if something is True. You can think of them as a kind of decision tree. Let's stick with the weather for an example.

If it's raining outside, then I need to grab an umbrella. If It's snowing, then I'll need a warm coat. Otherwise, I can bring a light jacket with me just in case.

Let's translate this into code!

if condition:
    # do something if this is true
    # this code must be after the colon :
    # and indented inside to run
elif condition:
    # do something if this condition is true
    # this code must be after the colon :
    # and indented inside to run
else:
    # if neither of the above two conditions is true, then run this
    # this code must be after the colon :
    # and indented inside to run

This is what conditionals look like in Python. You use == equals, > greater than, < less than, >=greater than or equal to,<=` less than or equal to create conditionals. There are other ways to create conditionals but these are the basics

The code you want to run when this condition is true is placed 'inside' the statement by closing the statement with a colon and then indenting the code on the following lines. Anything indented after the statement is considered a part of the conditional.

if weather == 'raining':
    # grab an umbrella

    # maybe grab some rain boots
    # even though there is an empty line, this is still indented and therefore a part of the above conditional
elif weather == 'snowing':
    # grab a warm coat
else:
    # grab a light jacket

Let's practice this with some numbers:

num = 5

if num < 3:
    print("It's less than 3")
elif num < 6:
    print("It's less than 6")
else:
    print("It's neither less than 3 nor less than 6")

In the above code, what will be printed out?

Let me know if you still need some more explanation

Jamshaid Ali
Jamshaid Ali
189 Points

what is a indented ?

Megan Amendola
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Megan Amendola
Treehouse Teacher
Megan Amendola
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Megan Amendola
Treehouse Teacher

Jamshaid Ali, indented is when you have either a tab or 4 spaces at the beginning of a line. Everything in Python works with indentations. In the example above, the print() statements are indented by 4 spaces and are therefore inside of the if, elif, and else statements.

# no indentation
num = 5

# no indentation
if num < 3:
    # indented
    print("It's less than 3")
# no indentation
elif num < 6:
    # indented
    print("It's less than 6")
# no indentation
else:
    # indented
    print("It's neither less than 3 nor less than 6")
Jamshaid Ali
Jamshaid Ali
189 Points
Jamshaid Ali
Jamshaid Ali
189 Points

Ahh ok great also i have 2 more questions, in the video Craig uses ".format" and he use "{}" as place holders can you explain what these two are and what they do

P.S thank you megan you have helped me alot!

Megan Amendola
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Megan Amendola
Treehouse Teacher
Megan Amendola
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Megan Amendola
Treehouse Teacher

Strings can be formatted. This is where you are able to pass in information to be placed inside of a string.

animal = 'dog'

# here you are formatting the string to place the string dog at the end of the sentence
print('My favorite animal is a {}'.format(animal))

>>> My favorite animal is a dog

# there are a few other ways to write this out
print('My favorite animal is a {pet}'.format(pet = animal))
print('My favorite animal is a {0}'.format(animal))


# You can place almost anything inside of a string using string formatting like a number

price = 5.99

# this will convert the float above into a string and place it inside of this string
print('The price is ${}'.format(price))

>>> The price is $5.99


# there is also a newer way of formating strings called f-strings

price = 5.99

# this does the same thing you just start with an f before the string and place the variable inside the curly brackets
print(f'The price is ${price}')

>>> The price is $5.99

# it also doesn't have to be a variable

print(f'The price is ${5.99}')
Jamshaid Ali
Jamshaid Ali
189 Points
Jamshaid Ali
Jamshaid Ali
189 Points

ahh ok thank you