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

Question

I am looking for a clean way to use variables within a multiline Python string. Say I wanted to do the following:

string1 = go
string2 = now
string3 = great

"""
I will $string1 there
I will go $string2
$string3
"""

I'm looking to see if there is something similar to $ in Perl to indicate a variable in the Python syntax.

If not - what is the cleanest way to create a multiline string with variables?

Answer 1

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.

Answer 2

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

Answer 3

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}."""

Answer 4

This is what you want:

>>> string1 = "go"
>>> string2 = "now"
>>> string3 = "great"
>>> mystring = """
... I will {string1} there
... I will go {string2}
... {string3}
... """
>>> locals()
{'__builtins__': <module '__builtin__' (built-in)>, 'string3': 'great', '__package__': None, 'mystring': "\nI will {string1} there\nI will go {string2}\n{string3}\n", '__name__': '__main__', 'string2': 'now', '__doc__': None, 'string1': 'go'}
>>> print(mystring.format(**locals()))

I will go there
I will go now
great

Answer 5

A dictionary can be passed to format(), each key name will become a variable for each associated value.

dict = {'string1': 'go',
        'string2': 'now',
        'string3': 'great'}

multiline_string = '''I'm will {string1} there
I will go {string2}
{string3}'''.format(**dict)

print(multiline_string)

Also a list can be passed to format(), the index number of each value will be used as variables in this case.

list = ['go',
        'now',
        'great']

multiline_string = '''I'm will {0} there
I will go {1}
{2}'''.format(*list)

print(multiline_string)

Both solutions above will output the same:

I'm will go there
I will go now
great