How do I create a multiline Python string with inline variables?

The common way is the format() function:

>>> s = "This is an {example} with {vars}".format(vars="variables", example="example")
>>> s
'This is an example with variables'

It works fine with a multi-line format string:

>>> s = '''\
... This is a {length} example.
... Here is a {ordinal} line.\
... '''.format(length='multi-line', ordinal='second')
>>> print(s)
This is a multi-line example.
Here is a second line.

You can also pass a dictionary with variables:

>>> d = { 'vars': "variables", 'example': "example" }
>>> s = "This is an {example} with {vars}"
>>> s.format(**d)
'This is an example with variables'

The closest thing to what you asked (in terms of syntax) are template strings. For example:

>>> from string import Template
>>> t = Template("This is an $example with $vars")
>>> t.substitute({ 'example': "example", 'vars': "variables"})
'This is an example with variables'

I should add though that the format() function is more common because it's readily available and it does not require an import line.

NOTE: The recommended way to do string formatting in Python is to use format(), as outlined in the accepted answer. I'm preserving this answer as an example of the C-style syntax that's also supported.

# NOTE: format() is a better choice!
string1 = "go"
string2 = "now"
string3 = "great"

s = """
I will %s there
I will go %s
%s
""" % (string1, string2, string3)

print(s)

Some reading:

• String formatting
• PEP 3101 -- Advanced String Formatting

You can use Python 3.6's f-strings for variables inside multi-line or lengthy single-line strings. You can manually specify newline characters using \n.

Variables in a multi-line string

string1 = "go"
string2 = "now"
string3 = "great"

multiline_string = (f"I will {string1} there\n"
                    f"I will go {string2}.\n"
                    f"{string3}.")

print(multiline_string)

I will go there
I will go now
great

Variables in a lengthy single-line string

string1 = "go"
string2 = "now"
string3 = "great"

singleline_string = (f"I will {string1} there. "
                     f"I will go {string2}. "
                     f"{string3}.")

print(singleline_string)

I will go there. I will go now. great.

---

Alternatively, you can also create a multiline f-string with triple quotes.

multiline_string = f"""I will {string1} there.
I will go {string2}.
{string3}."""

f-strings, also called “formatted string literals,” are string literals that have an f at the beginning; and curly braces containing expressions that will be replaced with their values.

f-strings are evaluated at runtime.

So your code can be re-written as:

string1="go"
string2="now"
string3="great"
print(f"""
I will {string1} there
I will go {string2}
{string3}
""")

And this will evaluate to:

I will go there
I will go now
great

You can learn more about it here.