python string u“％（word）s”

Question

I'm a new user of Python, and I don't know some parts when I read the code. So I asked here.

cmd = u"sudo umount %(mountpoint)s >>%(log)s 2>&1"

I know that %(word) is used to replace the word latter use such as cmd % {'word':'new word'} , but I don't down why there is a trailing s . and I don't know the 'u' meaning at the beginning of the string.

Answer 1

The beginning u means "Unicode" (ie it's a Unicode string). The s after each formatting code means to interpret the value as a string, as opposed to d for decimal, etc.

See the documentation at http://docs.python.org/library/stdtypes.html#string-formatting-operations for all the details.

Answer 2

The u at the beginning of the string means that it's a unicode string.

The trailing s means that that part of the formatting should be a string. If it was aad it would be an integer, and if it was an f it would be a float

Answer 3

1. u means it is a unicode string.
2. s stands for string.

Answer 4

s is a conversion specifier, meaning print it as a string.

See string formatting , point 3:

Conversion flags (optional), which affect the result of some conversion types.

The leading u means it is a unicode object, not a str .

See Unicode in Python, Completely Demystified for a great overview of the difference between the two.