Printing a string prints 'u' before the string in Python?

问题

'u' before elements in printed list? I didn't type u in my code.

hobbies = []

#prompt user three times for hobbies
for i in range(3):
    hobby = raw_input('Enter a hobby:')
    hobbies.append(hobby)

#print list stored in hobbies
print hobbies

When I run this, it prints the list but it is formatted like this:

Enter a hobby: Painting
Enter a hobby: Stargazing
Enter a hobby: Reading
[u'Painting', u'Stargazing', u'Reading']
None

Where did those 'u' come from before each of the elements of the list?

回答1:

I think what you're actually surprised by here is that printing a single string doesn't do the same thing as printing a list of strings—and this is true whether they're Unicode or not:

>>> hobby1 = u'Dizziness'
>>> hobby2 = u'Vértigo'
>>> hobbies = [hobby1, hobby2]
>>> print hobby1
Dizziness
>>> print hobbies
[u'Dizziness', u'V\xe9rtigo']

Even without the u, you've got those extra quotes, not to mention that backslash escape. And if you try the same thing with str byte strings instead of unicode strings, you'll still have the quotes and escapes (plus you might have mojibake characters if your source file and your terminal have different encodings… but forget that part).

---

In Python, every object can have two different representations: the end-user-friendly representation, str, and the programmer-friendly representation, repr. For byte strings, those representations are Painting and 'Painting', respectively. And for Unicode strings, they're Painting and u'Painting'.

The print statement uses the str, so print hobby1 prints out Painting, with no quotes (or u, if it's Unicode).

However, the str of a list uses the repr of each of its elements, not the str. So, when you print hobbies, each element has quotes around it (and a u if it's Unicode).

This may seem weird at first, but it's an intentional design decision, and it makes sense once you get used to it. And it would be ambiguous to print out [foo, bar, baz]—is that a list of three strings, or a list of two strings, one of which has a comma in the middle of it? But, more importantly, a list is already not a user-friendly thing, no matter how you print it out. My hobbies are [Painting, Stargazing] would look just as ugly as My hobbies are ['Painting', 'Stargazing']. When you want to show a list to an end-user, you always want to format it explicitly in some way that makes sense.

Often, what you want is as simple as this:

>>> print 'Hobbies:', ', '.join(hobbies)
Hobbies: Painting, Stargazing

Or, for Unicode strings:

>>> print u'Hobbies:', u', '.join(hobbies)
Hobbies: Painting, Stargazing

回答2:

The 'u' is not part of the string, but indicates that the string is a unicode string.

回答3:

You're not printing the strings, you're printing the representation of the list holding the strings.

for hobby in hobbies:
  print hobby

回答4:

If you want to convert the unicode to string. You can simply use str(unicodedString) or unicode(normalString) for the other way conversion

Code

hobbies = []

#prompt user three times for hobbies
for i in range(3):
    hobby = raw_input('Enter a hobby:')
    # converting the normal string to unicode
    hobbies.append(unicode(hobby))

# Printing the unicoded string
print("Unicoded string")
print(hobbies)
hobbies = [str(items) for items in hobbies]

# Printing the converted string
print("Normal string from unicoded string")
print(hobbies)

Output

Enter a hobby:test1
Enter a hobby:Test2
Enter a hobby:Test3

Unicoded string
[u'test1', u'Test2', u'Test3']

Normal string from unicoded string
['test1', 'Test2', 'Test3']

来源：https://stackoverflow.com/questions/19170808/printing-a-string-prints-u-before-the-string-in-python