- Author:
- atombrella
- Posted:
- January 25, 2017
- Language:
- Python
- Version:
- Not specified
- Score:
- 0 (after 0 ratings)
Small example of how to write your own function. This is not available in Django. The function just replaces static text strings, regular expressions are not supported.
The syntax is the same in SQLite, PostgreSQL, MySQL and Oracle.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | from django.db.models import F, Func, Value
class Replace(Func):
function = 'REPLACE'
def __init__(self, expression, text, replacement=None):
if not hasattr(expression, 'resolve_expression'):
raise ValueError('Please pass a valid expression')
if text is None:
raise ValueError('Replacing null does not seem sane ...')
self.text = Value(text)
self.replacement = Value('' if replacement is None else replacement)
self.expression = expression
super().__init__(self.expression, self.text, self.replacement)
# it's then possible to use it to replace text in expressions:
Customer.objects.filter(name='Bert').update(name=Replace(F('name'), 'Bert', 'Ernie')
|
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