请求大神帮看一下代码，python的

@login_required
@require_POST
def share_repo(request):

"""
Handle POST method to share a repo to public/groups/users based on form
data. Return to ``myhome`` page and notify user whether success or failure.
"""
next = request.META.get('HTTP_REFERER', None)
if not next:
    next = SITE_ROOT

form = RepoShareForm(request.POST)
if not form.is_valid():
    # TODO: may display error msg on form
    raise Http404

email_or_group = form.cleaned_data['email_or_group']
repo_id = form.cleaned_data['repo_id']
permission = form.cleaned_data['permission']

repo = seafile_api.get_repo(repo_id)
if not repo:
    raise Http404

# Test whether user is the repo owner.
username = request.user.username
if not seafile_api.is_repo_owner(username, repo_id) and \
        not is_org_repo_owner(username, repo_id):
    msg = _(u'Only the owner of the library has permission to share it.')
    messages.error(request, msg)
    return HttpResponseRedirect(next)

# Parsing input values.
share_to_all, share_to_groups, share_to_users = False, [], []
user_groups = request.user.joined_groups
share_to_list = string2list(email_or_group)
for share_to in share_to_list:
    if share_to == 'all':
        share_to_all = True
    #elif share_to.find('@') == -1:
    elif share_to[0] == '%':
        for user_group in user_groups:
            if user_group.group_name == share_to[1:]:
                share_to_groups.append(user_group)
    else:
        share_to = share_to.lower()
        if is_valid_username(share_to):
            share_to_users.append(share_to)

if share_to_all:
    share_to_public(request, repo, permission)

if not check_user_share_quota(username, repo, users=share_to_users,
                              groups=share_to_groups):
    messages.error(request, _('Failed to share "%s", no enough quota. <a href="http://www.i2cloud.cn/">Upgrade account.</a>') % repo.name)
    return HttpResponseRedirect(next)

for group in share_to_groups:
    share_to_group(request, repo, group, permission)

for email in share_to_users:
    # Add email to contacts.
    mail_sended.send(sender=None, user=request.user.username, email=email)
    share_to_user(request, repo, email, permission)

return HttpResponseRedirect(next)

上面的代码中的

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这是判断语句
A = 1
B = 2
if A<3:

print A

elif B>2:

print B

如果A小于3，输出A的值1;如果B大于3，输出B的值2

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第一个是在匹配固定格式...
后面那个冒号是python条件判断表达式的语法...

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关键字 python 分片