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Python | Iterate through value lists dictionary
• Last Updated : 26 Jul, 2019

While working with dictionary, we can have a case in which we need to iterate through the lists, which are in the keys of dictionaries. This kind of problem can occur in web development domain. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using list comprehension
List comprehension can be used to perform this particular task. It is just the shorthand to the conventional nested loops. we iterate for each key’s list and store the result.

 `# Python3 code to demonstrate working of``# Iterating through value lists dictionary``# Using list comprehension`` ` `# Initialize dictionary``test_dict ``=` `{``'gfg'` `: [``1``, ``2``], ``'is'` `: [``4``, ``5``], ``'best'` `: [``7``, ``8``]}`` ` `# printing original dictionary``print``(``"The original dictionary : "` `+`  `str``(test_dict))`` ` `# Using list comprehension``# Iterating through value lists dictionary``res ``=` `[[i ``for` `i ``in` `test_dict[x]] ``for` `x ``in` `test_dict.keys()]``     ` `# printing result ``print``(``"The list values of keys are : "` `+` `str``(res))`
Output :

The original dictionary : {‘best’: [7, 8], ‘is’: [4, 5], ‘gfg’: [1, 2]}
The list values of keys are : [[7, 8], [4, 5], [1, 2]]

Method #2 : Using `from_iterable() + product() + items()`
The combination of above functions can be used to perform this particular task. The `from_iterable()` can be used to reduce inner loop and `items` function is used to extract key value pairs in the dictionary.

 `# Python3 code to demonstrate working of``# Iterating through value lists dictionary``# Using from_iterable() + product() + items()``import` `itertools`` ` `# Initialize dictionary``test_dict ``=` `{``'gfg'` `: [``1``, ``2``], ``'is'` `: [``4``, ``5``], ``'best'` `: [``7``, ``8``]}`` ` `# printing original dictionary``print``(``"The original dictionary : "` `+`  `str``(test_dict))`` ` `# Iterating through value lists dictionary``# Using from_iterable() + product() + items()``res ``=` `[]``for` `key, value ``in` `(``        ``itertools.chain.from_iterable(``            ``[itertools.product((k, ), v) ``for` `k, v ``in` `test_dict.items()])):``                ``res.append(value)``     ` `# printing result ``print``(``"The list values of keys are : "` `+` `str``(res))`
Output :

The original dictionary : {‘best’: [7, 8], ‘is’: [4, 5], ‘gfg’: [1, 2]}
The list values of keys are : [7, 8, 1, 2, 4, 5]

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