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This tutorial demonstrates how to check if a value exists in a Python dictionary. Here, we will cover related topics such as searching for a value given by a key, searching for a specific value, and searching for the value of an object or collection.

First, we need to print if the value exists in the dictionary True; otherwise, print it False.

get()Check if a value exists in a dictionary using and key

Dictionaries in Python have a built-in function key()that returns the value for a given key. At the same time, if it does not exist, it will return None. You can use this function as a condition to determine if a value exists in a dictionary.

Let's start by declaring a simple dictionary with intkeys and string values.

simpDict = {1: "Ant", 2: "Bear", 3: "Cat", 4: "Dog", 5: "Elephant"}

If you want to find a value using its key pair, then key()the function is the best way to do it. For example, you want to search for any value with 6 as the key; follow the code below.

if simpDict.key(6) != None:
    print("True")
else:
    print("False")

Since simpDictthe function does not have a key 6, this code will output False.

Use values()to check if the specified value exists in the dictionary

Unlike the case of looking for a specific value, looking for a key in a dictionary is very straightforward; you just use the keyword inand the key you want to look for in the dictionary.

print(3 in simpDict)

This will print True, because the key 3 exists. If we replace the number with a key that doesn't exist, then it will print False.

On the other hand, if you want to find a specific value in a dictionary, you can use the function values(). values()The command will return a list of all the values ​​in the dictionary. Using values(), you can inquery the dictionary and the specified value using the keyword. Suppose you want to know Elephantwhether the value is in the dictionary, execute the following code.

print("Elephant" in simpDict.values())

This line will be output Truebecause the word simpDictexists in key 5 .Elephant

In Python 2.X, there are two values()functions similar to , which are itervalues()and viewvalues(); these functions have been deprecated in Python 3.X version.

itervalues()The and viewvalues()commands will values()accomplish the same task as the command; however, the different implementations, while very minor, significantly affect the runtime.

print("Elephant" in simpDict.itervalues())
print("Elephant" in simpDict.viewvalues())

Both return values()the same output as the function. It is important to note that redundancy is probably the main reason these functions are deprecated from newer Python versions.

Now, what if the values ​​in the dictionary are data structures like lists or objects? Let’s see.

If the value is a list, check if the value exists in a dictionary

listDict = {1: ["a", "b"], 2: ["b", "c"], 3: ["c", "d"], 4: ["d", "e"]}

Now, we have a intdictionary with keys and a list of characters as values.

Suppose we want to search ['c', 'd']whether a list exists in a dictionary.

print(["c", "d"] in listDict.values())

The resulting output will be True; this confirms that iterating over dictionaries to compare sets is also possible.

But what if you want to check if one of the values ​​in the list exists in the dictionary? To fix this, just loop over the values ​​and use inthe keyword on the list instead of on the dictionary.

For example, you want to check 'e'if a character is present in the value in this list. Here is the code to execute.

tof = False
for value in listDict.values():
    if "e" in value:
        tof = True
        break
print(tof)

The output will print out Trueas 'e'exists in the dictionary.

In summary, use the function values()to iterate over the values ​​and compare if the value you are looking for exists in the list of values. This is helpful when you want to check if a specific value exists in a dictionary.