Python Jinja2 Loop Dict

Jinja2 is a powerful templating engine for Python, widely used in web development frameworks such as Flask and Django. It allows you to generate dynamic content by rendering templates with variables, conditions, and loops. One of the most useful features of Jinja2 is the ability to loop over a dictionary.

To loop over a dictionary in Jinja2, you can use the for loop construct. Here's an example:

{% for key, value in my_dict.items() %}
    Key: {{ key }}, Value: {{ value }}
{% endfor %}

In the above code snippet, my_dict is a dictionary object. Using the items() method, we can iterate over the key-value pairs of the dictionary. Inside the loop, we can access the key with {{ key }} and the value with {{ value }}.

You can perform various operations within the loop, such as conditional statements and nested loops. Here's an example that demonstrates a nested loop:

{% for key, sub_dict in my_dict.items() %}
    Key: {{ key }}
    {% for sub_key, value in sub_dict.items() %}
        Sub Key: {{ sub_key }}, Value: {{ value }}
    {% endfor %}
{% endfor %}

In the above code snippet, my_dict is a dictionary that contains sub-dictionaries. We iterate over the main dictionary using the first for loop and then iterate over each sub-dictionary using the second for loop.

Jinja2 also provides several useful filters and functions that can be used within the loop. For example:

• loop.index: Returns the current iteration index (1-based).
• loop.index0: Returns the current iteration index (0-based).
• loop.first: Returns True if it's the first iteration.
• loop.last: Returns True if it's the last iteration.

{% for key, value in my_dict.items() %}
    Index: {{ loop.index }}, Key: {{ key }}, Value: {{ value }}
{% endfor %}

This code snippet demonstrates the usage of the loop.index filter to display the iteration index.

In conclusion, Jinja2 provides an easy and flexible way to loop over dictionaries in Python. It allows you to generate dynamic content based on the key-value pairs of a dictionary, perform nested loops and conditional statements, and use various filters and functions to customize the output. It is a powerful tool for generating dynamic templates in web development.