词法分析python

Question

Recently I made the following observation:

>>> x= "\'"
>>> x
"'"
>>> y="'"
>>> y
"'"
>>> print x
'
>>> print y
'

Can anyone please explain why is it so. I am using python 2.7.x. I know well about escape sequences.

I want to do the following: I have a string with single quotes in it and I have to enter it in a database so I need to replace the instance of single quote(') with a backslash followed by a single quote(\\'). How can I achieve this.

Answer 1

Inside a pair of "" , you don't need to escape the ' character. You can, of course, but as you've seen it's unnecessary and has no effect whatsoever.

It'd be necessary to escape if you were to write a ' inside a pair of '' or a " inside a pair of "" :

x = '\''
y = "\""

EDIT :

Regarding the last part in the question, added after the edit:

I have a string with single quotes in it and I have to enter it in a database so I need to replace the instance of single quote(') with a backslash followed by a single quote(\\'). How can I achieve this

Any of the following will work, notice the use of raw strings for avoiding the need to escape special characters:

v = "\\'"
w = '\\\''
x = r'\''
y = r"\'"

print v, w, x, y
> \' \' \' \'