# Could not open a connection to your authentication agent
eval `ssh-agent -s`

# ssh remote port forwarding
```shell
ssh -nNT -L 9000:ifconfig.me:80 mords
```

# django import config
```python
from django.conf import settings

if settings.DEBUG:
    # Do something
```

# python strftime

# python strptime

# django send mail
In two lines:
```python
from django.core.mail import send_mail

send_mail(
    'Subject here',
    'Here is the message.',
    'from@example.com',
    ['to@example.com'],
    fail_silently=False,
)
```
```
EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'
EMAIL_HOST = 'smtp.exmail.qq.com'
EMAIL_HOST_USER = 'sys@yourdomain.com'
EMAIL_HOST_PASSWORD = 'youpass'
EMAIL_TIMEOUT = 10
```

# django field lookup
isnull
Takes either True or False, which correspond to SQL queries of IS NULL and IS NOT NULL, respectively.
```python
Entry.objects.filter(pub_date__isnull=True)
```
```SQL
SELECT ... WHERE pub_date IS NULL;
```
# django annotate
```python
from django.db.models import Sum

Title.objects.values('publisher').annotate(tot_dbl_prices=2*Sum('price'))
```

# python defaultdict
```python
from collections import defaultdict

s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
d = defaultdict(list)
for k, v in s:
     d[k].append(v)
d.items()
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]
```

# mysql create user and grant permission
```sql
CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'password';
GRANT type_of_permission ON database_name.table_name TO ‘username’@'localhost’;
GRANT ALL PRIVILEGES ON * . * TO 'newuser'@'localhost';
```