Snippet List
This math captcha field and widget was inspired by Justin Quick's django-math-captcha, but I wanted to make it into one form field and not have anything in settings.py. I removed the division and modulo operators to avoid people having to input fractions, and just randomly select the operator.
It leverages Django's built-in MultiValueField to set up the hidden hashed answer to compare the user's input to instead of rendering strings for the fields like django-math-captcha does.
Unit tests soon to follow, but this is used in production at: http://btaylorweb.com/. Enjoy!
- simple
- captcha
- field
- widget
- math
- multiwidget
- multifield
Syntax:
{% math <argument, ..> "expression" as var_name %}
Evaluates a math expression in the current context and saves the value into a variable with the given name.
"$<number>" is a placeholder in the math expression. It will be replaced by the value of the argument at index <number> - 1.
Arguments are static values or variables immediately after 'math' tag and before the expression (the third last token).
Example usage,
{% math a b "min($1, $2)" as result %}
{% math a|length b|length 3 "($1 + $2) % $3" as result %}
This FloatField replacement allows users to enter math expressions, such as:
4/5 + sqrt(32)
And will evaluate them safely when the field's clean() function is called. In the example above, it will evaluate to a float value of about 6.457.
Reference:
[http://lybniz2.sourceforge.net/safeeval.html](http://lybniz2.sourceforge.net/safeeval.html)
The available functions are listed herein. Note that the from __future__ import division causes integer division expressions to be evaluated as floats. For example "1/2" evaluates as 0.5 when it would otherwise have evaluated to 0 (assuming Python 2.X).
- fields
- forms
- parser
- math
- eval
- parsing
- floatfield
I have a need to conditionally format a negative number, a hedgefund's daily price change, Excel style. i.e. show a negative number as a parenthesized number instead of a negative sign. Here is a filter that will do that and more, solving a more general case. See the doctest for examples.
- template
- filter
- format
- currency
- math
Formats float values with specified number of significant digits (defaults to 3).
Usage:
`{{value|sigdig}} # with 3 significant digits by default`
`{{value|sigdig:digits}}`
Examples:
`{{0.001432143|sigdig}}` renders as `0.00143`
`{{874321.4327184|sigdig}}` renders as `874000`
`{{874321.4327184|sigdig:5}}` renders as `874320`
Useful for scientific or engineering presentation.
- filter
- filters
- math
- engineering
Django's templates don't provide much in the way of arithmetic: there is an "add" filter and that is about it. Even if sub, mult and div filters are implemented, it is difficult to chain filters while preserving some complicated expression, such as ((x+3)4-(2-y)/12.75). However, this expression can be converted into Reverse Polish Notation: x 3 + 4 * 2 y - 12.75 / - which is just a sequence of operations (push-value or apply-operator) and can be chained.
To use these filters, first create a new stack for the expression with name|stnew (pass it some locally unique value). To push a number (or template variable) onto the stack, call name|stpush:number (note that you have to tell stpush the name of the stack to push onto). To pop, call name|stpop. To perform an operation, call name|st[add,sub,mult,div,mod]:number. All numbers are integers if they look like integers, or floats otherwise (integers are turned into floats upon division if they need to be). All of these functions return the name of the stack so that they can be chained. When the calculation is finished (i.e. the answer is at the bottom of the stack) call name|stget to retrieve it.
Example (this was used to calculate an inline CSS value:
`left: {{ forloop.counter|stnew|stpush:res.stwkday|stpush:"9.35"|stmult|stpush:res.get_item_left|stpush:"2.75"|stadd|stadd|stget }}em;`
- template
- filter
- math
- arithmetic
- rpn
- reverse-polish-notation
7 snippets posted so far.