使用Python检查列表中是否存在字符串元素？

Question

I have the following piece of code:

self.ignore_dir_extensions = ['xcodeproj']

item = repr(extension.split('/')[0])

print "String: " + item

if item in self.ignore_dir_extensions:
    print "Available: " + item

Let's say I have this output:

String: 'xcodeproj'

Expected output:

String: 'xcodeproj'
Available: 'xcodeproj'

Could anyone help me out here?

Answer 1

Try the following:

self.ignore_dir_extensions = ['xcodeproj']

item = extension.split('/')[0]

print "String: " + repr(item)

if item in self.ignore_dir_extensions:
    print "Available: " + repr(item)

You do not want to have item be the result of repr() , because repr() on a string will add quotes, for example:

>>> repr("xcodeproj")
"'xcodeproj'"
>>> print repr("xcodeproj")
'xcodeproj'
>>> print "xcodeproj"
xcodeproj

When you are checking to see if the string exists in the list, you don't want the quotes unless the string you are trying to match also has them.

Answer 2

Your test for is-string-contained-in-list is correct. However, you are testing for the presence of a different string than you intended. You called repr on your string, so the name item is bound to the string "'xcodeproj'" (not to the string "xcodeproj" ).

Answer 3

I would personally do this:

self.ignore_dir_extensions = ['xcodeproj']

item = repr(extension.split('/')[0])

print "String: " + item

try:
    self.ignore_dir_extensions.index(item)
    print "Available: " + item
except:
    pass

Answer 4

you can simply use:

item = extension.split('/')[0]

print "String: '%s'" % item

if item in self.ignore_dir_extensions:
    print "Available: '%s'" %` item

this way you avoid the problems with repr