String Formatting

Python uses C-style string formatting to create new, formatted strings. The "%" operator is used to format a set of variables enclosed in a "tuple" (a fixed size list), together with a format string, which contains normal text together with "argument specifiers", special symbols like "%s" and "%d".

Let's say you have a variable called "name" with your user name in it, and you would then like to print(out a greeting to that user.)

# This prints out "Hello, John!"
name = "John"
print("Hello, %s!" % name)

To use two or more argument specifiers, use a tuple (parentheses):

# This prints out "John is 23 years old."
name = "John"
age = 23
print("%s is %d years old." % (name, age))

Any object which is not a string can be formatted using the %s operator as well. The string which returns from the "repr" method of that object is formatted as the string. For example:

# This prints out: A list: [1, 2, 3]
mylist = [1,2,3]
print("A list: %s" % mylist)

Here are some basic argument specifiers you should know:

%s - String (or any object with a string representation, like numbers)

%d - Integers

%f - Floating point numbers

%.<number of digits>f - Floating point numbers with a fixed amount of digits to the right of the dot.

%x/%X - Integers in hex representation (lowercase/uppercase)

Exercise

You will need to write a format string which prints out the data using the following syntax: Hello John Doe. Your current balance is $53.44.

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