String concatenation and f strings

Key ideas

• Using formatted strings
• Concatenating strings

String Concatenation and f-strings

When there’s a variable we want to combine with a string to print out a message, so far we’ve added the strings with +.

name = "Mercy"
print("Hello, " + name) # Hello, Mercy

When the message is longer, this becomes more confusing and harder to type.

name = "Mercy"
print("The alarm went off at exactly 6:00 AM as it had every morning for the past five years. " + name + " began her morning and was ready to eat breakfast by 7:00 AM. The day appeared to be as normal as any other, and " + name + " was not expecting anything to change.")

There’s another way to format long text that uses variables, called f-strings.

name = "Mercy"
print(f"Hello, {name}") # Hello, Mercy
print(f"The alarm went off at exactly 6:00 AM as it had every morning for the past five years. {name} began her morning and was ready to eat breakfast by 7:00 AM. The day appeared to be as normal as any other, and {name} was not expecting anything to change.")

Instead of using + to combine the variable and the string, we start the string with f and we use {} to insert the variable right inside the string. That way, there’s less confusion about quote marks and spaces.

Check the following video on how to check some commands using python console.

Other f-string uses

We can also use f-strings for rounding.

one_third = 1/3
print(one_third)# 0.3333333333333333
print(f"{one_third:.2}") # 0.33

f-strings have other formatting powers, but we’ll leave it at rounding floats for now.

Practice: f-strings

Open a new file in VSCode to practice with f-strings.

• Try printing some messages using f-strings and variables
• Try rounding a float to a specific number of digit

Looking at the f-strings documentation, what other tricks do you want to try? If you find something you think is particularly useful or interesting, share it with your classmates in Discord.

first_num = float(input("enter first number: "))
second_num = float(input("enter second number: "))

result = first_num / second_num

print(f"the result is {result:.3} ")