python中的双引号和单引号

Question

hello I am currently learning python and I've been stuck in this small script thats written in my ebook.

formatter = "%r %r %r %r"

print formatter %(1, 2, 3, 4)
print formatter %("one", "two", "three", "four")
print formatter %(True, False, False, True)
print formatter %(formatter, formatter, formatter, formatter)
print formatter %(
    "I had this thing.",
    "That you could type up right.",
    "But it didn't sing.",
    "So I said goodnight."
)

When I run the code every other string is in single quotes but the "But it didn't sing" is in double quotes. After trying several syntax i understood that the single quote in didn't has something to do with this. But why does this happen? If I assign that line to a variable and print it like

yathartha = "But it didn't happen"
print "%r" %yathartha 

the output is "But it didn't happen" with the double quotes. Isn't there supposed to be single quote?

Answer 1

Well, when you are talking about a string, it is present between the quotes, so if your string contains a single quote, it can't use single quotes to enclose it because, if it starts with a single quote, it'll end at the first single quote.

yathartha = "But it didn't happen"
string_var = "%r" %yathartha 
print string_var

If your string was enclosed in single quotes then your string which would get stored in string_var would be 'But it didn' because that would be the closing quote that it encounters.