Format Specifier

What is a Format Specifier?#

A format specifier in Python provides a mechanism to control the exact display of values as strings. It enables the programmer to define the type of data and its presentation style. Python uses the % operator as a placeholder for a format specifier.

1print("Hello, I am %s and I am %d years old." % ('Dino', 32)) 

The above example features two format specifiers, %s and %d which stand for string and decimal integer respectively. The names and age are inserted in place of these specifiers, following the % operator.

Different Types of Format Specifiers#

There are various types of format specifiers in Python. Here are a few examples:

• %s: string
• %d: decimal integer
• %f: float
• %.nf: float rounded off to ’n’ decimal places
• %x: hexadecimal
• %o: octal

1print("Decimal: %d \nString: %s \nFloat: %f \nHex: %x \nOct: %o" % (15, 'Hello', 9.6, 255, 15))

Precision in Format Specifier#

Format specifier allows controlling the precision of floating point numbers. The precision is the number of digits after the decimal point.

You can use %.nf, where n is the desired number of decimal places.

1print("Pi value with 2 decimal places: %.2f" %(3.14159)) 

The above code prints the value of pi up to two decimal places.

Using Format Specifier with Dictionary#

You can also use format specifiers with dictionaries. All you need to do is include the index or key in parentheses, preceded by a percent sign.

1name_and_age = {"name":"Anna","age": 27}
2print("Hello, I am %(name)s and I am %(age)d years old." % name_and_age)

The above code fetches the values from the dictionary and inserts them in the specified places in the string.