Is there any way to use variables in multiline string in Python?

Question

So I have this as part of a mail sending script:

try:
    content = ("""From: Fromname <fromemail>
    To: Toname <toemail>
    MIME-Version: 1.0
    Content-type: text/html
    Subject: test

    This is an e-mail message to be sent in HTML format

    <b>This is HTML message.</b>
    <h1>This is headline.</h1>
    """)

...

    mail.sendmail('from', 'to', content)

And I'd like to use different subjects each time (let's say it's the function argument).

I know there are several ways to do this.

However, I am also using ProbLog for some of my other scripts (a probabilistic programming language based in Prolog syntax). As far as I know, the only way to use ProbLog in Python is through strings, and if the string is broke in several parts; example = ("""string""", variable, """string2"""), as well as in the email example above, there's no way I can make it work.

I actually have a few more scripts where using variables in multiline strings could be useful, but you get the idea.

Is there any way to make this work? Thanks in advance!

You appear to want a multi-line `String`, not a multi-line comment. Using a variable in a comment wouldn't make any sense - comments aren't executed. — Elliott Frisch, Mar 09 '16 at 21:33
Python doesn't _have_ multi-line comments. Triple-quoted strings are **not** comments. — PM 2Ring, Mar 09 '16 at 21:47
That's right. Sorry. Multiline strings. I'm new into python. I just didn't thought about it. — , Mar 09 '16 at 21:48
This question was incorrectly marked as a duplicate of http://stackoverflow.com/questions/517355 ... this question is not a duplicate because the other question does not refer to using multi-line strings — dreftymac, Mar 09 '16 at 22:13

L3viathan · Accepted Answer · 2020-07-13T05:33:31.550

Using the .format method:

content = """From: Fromname <fromemail>
    To: {toname} <{toemail}>
    MIME-Version: 1.0
    Content-type: text/html
    Subject: {subject}

    This is an e-mail message to be sent in HTML format

    <b>This is HTML message.</b>
    <h1>This is headline.</h1>
"""
mail.sendmail('from', 'to', content.format(toname="Peter", toemail="p@tr", subject="Hi"))

Once that last line gets too long, you can instead create a dictionary and unpack it:

peter_mail = {
    "toname": "Peter",
    "toemail": "p@tr",
    "subject": "Hi",
}
mail.sendmail('from', 'to', content.format(**peter_mail))

As of Python 3.6, you can also use multi-line f-strings:

toname = "Peter"
toemail = "p@tr"
subject = "Hi"
content = f"""From: Fromname <fromemail>
    To: {toname} <{toemail}>
    MIME-Version: 1.0
    Content-type: text/html
    Subject: {subject}

    This is an e-mail message to be sent in HTML format

    <b>This is HTML message.</b>
    <h1>This is headline.</h1>
"""

Is there any way to use variables in multiline string in Python?

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