Related Articles
Python | Search Key from Value
• Last Updated : 07 Jul, 2019

The problem of finding a value from a given key is quite common. But we may have a problem in which we wish to get the back key from the input key we feed. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using Naive Method
In this method, we just run a loop for each of the values and return the corresponding key or keys whose value match. This is the brute force way to perform this particular task.

 `# Python3 code to demonstrate working of ` `# Search Key from Value ` `# Using naive method ` ` `  `# initializing dictionary ` `test_dict ``=` `{``'Gfg'` `: ``1``, ``'for'` `: ``2``, ``'CS'` `: ``3``} ` ` `  `# printing original dictionary ` `print``(``"The original dictionary is : "` `+` `str``(test_dict)) ` ` `  `# initializing value ` `val ``=` `3` ` `  `# Using naive method  ` `# Search key from Value ` `for` `key ``in` `test_dict: ` `    ``if` `test_dict[key] ``=``=` `val: ` `        ``res ``=` `key ` ` `  `# printing result  ` `print``(``"The key correspoding to value : "` `+` `str``(res)) `

Output :

```The original dictionary is : {'CS': 3, 'for': 2, 'Gfg': 1}
The key correspoding to value : CS
```

Method #2 : Using `items()` + list comprehension
This problem can be easily solved using the `items()`, which is used to extract both keys and values at once, hence making the search easy and can be executed using list comprehension making it a one liner.

 `# Python3 code to demonstrate working of ` `# Search Key from Value ` `# Using items() + list comprehension ` ` `  `# initializing dictionary ` `test_dict ``=` `{``'Gfg'` `: ``1``, ``'for'` `: ``2``, ``'CS'` `: ``3``} ` ` `  `# printing original dictionary ` `print``(``"The original dictionary is : "` `+` `str``(test_dict)) ` ` `  `# initializing value ` `val ``=` `3` ` `  `# Using items() + list comprehension ` `# Search key from Value ` `res ``=` `[key ``for` `key, value ``in` `test_dict.items() ``if` `value ``=``=` `val] ` ` `  `# printing result  ` `print``(``"The key correspoding to value : "` `+` `str``(res)) `

Output :

```The original dictionary is : {'CS': 3, 'for': 2, 'Gfg': 1}
The key correspoding to value : ['CS']
```

Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course.

My Personal Notes arrow_drop_up
Recommended Articles
Page :