Use cases
Printing variables
In python, we usually print variables using format( ) method by passing values of the variable as its argument.
platform="Coding Ninjas Studio"
print("welcome to the {}".format(platform));

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Output
welcome to the Coding Ninjas Studio
Above requirement can be fulfilled easily by just using f-string. In that case, we don’t need to use any function to format the string for printing.
platform="Coding Ninjas Studio"
print(f"welcome to the {platform}")

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Output
welcome to the Coding Ninjas Studio
In the above example, the variable platform is replaced with Coding Ninjas Studio .
Evaluating expression
It can also be used for evaluating the expression while printing its value as the expression is evaluated during runtime.
val1=10
val2=20
print(f"product of val1 and val2 : {val1*val2}")

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Output
product of val1 and val2 : 200
Conditional statement
F-string is also used with conditional if…else statement.
val1=10
val2=20
print(f"product of val1 and val2 is greater than 100 :{True if val1*val2>100 else False}")

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Output
product of val1 and val2 is greater than 100 :True
F-string with Function
Function can be called inside a f-string. If the function returning any string that string will be concatenated with the remaining f-string.
def evaluate(num):
if(num>100):
return f"{num} is greater than 100"
else :
return f"{num} is not greater than 100"
print(f"result of evaluation: {evaluate(50)}")

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Output
result of evaluation: 50 is not greater than 100
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FAQs
Q1. Is f-string is faster than the format( ) method for formatting a string?
Ans.
Yes, f-string is faster in formatting a string.
Q2. How f-string is used to justify string while printing?
Ans.
By default, a string is justified to left. To justify a string to left > character is used. It follows the colon character.
s1='c'
s2='cd'
s3='cde'
print(f"{s1:>5}")#width of the output set to 5 characters
print(f"{s2:>5}")
print(f"{s3:>5}")

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Output
c
cd
cde
Q3. How f-string is formatted using f-string?
num=2.5
print(f"{num:.3f}") # precision value 3 is mentioned
##output
2.500

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Q4. How to format date-time using f-string?
import datetime
now= datetime.datetime.now()
print(f"{now:%Y-%m-%d %H:%M}")
##output
2022-02-05 06:44

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Key Takeaways
This article covered how to format string using f-string and where it can be used.
Check out the Coding Ninjas Studio Guided Path on Python programming for learning Python language from basics.
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