如何在 flask 模板中对变量执行数学运算

Question

I just need to perform this

{% i += 1 %}

but I end with this error

jinja2.exceptions.TemplateSyntaxError:
       expected token 'end of statement block', got '+'

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problem is to perform a math operation within a loop and every time the variable should change.. not printing it

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edit

I reached this point {% set i = sum([i, 1]) %}

but within for loop it prints 111111111 not 123456789 '_'

Answer 1

try to do the following code, just do the math operation before. it worked for me.

i+=1
return render_template("file.html",i=i)

And write in your html file the following line:

<p>{{i}}</p>

Answer 2

Jinja math operations does not allow the operator += . You can see the available operators here

You can do something like

{% set count =  i + 1 %}

Given i is already a defined variable.