CODEWITHSUNDEEP
pythonpython-2.7dictionary
Siddhartha
Siddhartha

Reputation: 113

Examining the working of cmp function for dictionaries

Consider two dictionaries as follows:

d1={"Name":"John","Age":47}
d2={"Name":"Margaret","Age":35}

On executing the following statement:

>>>cmp(d1,d2)
1

That implies that since the keys are identical therefore it compares the values and gives priority to the value associated with the "Age" key (perhaps because lexicographically it comes first). This is supported by the fact that when I alter the dictionaries:

d1={"Name":"John","Age":47}
d2={"Name":"Jack","Age":47}

The statement returns 1. Since the sum of the ASCII values is greater for d1.

But consider this pair of dictionaries:

d1={"Name":"John","Age":47}
d2={"Name":"Jzan","Age":47}

Now the statement returns -1. Why is that? Is it that instead of comparing the sum of the ASCII values, it compares each character's value, one by one? Also, if the keys themselves are different, on what basis does the function compare?

Upvotes: 0

Views: 80

Answers (1)

Haochen Wu
Haochen Wu

Reputation: 1823

Most of the programming language implement the comparison of strings according to dictionary order (the way that words are ordered in a dictionary), i.e. compare the character's value one by one and return the first difference.

If the keys themselves are different, the return values are actually depends on the implementation. You can find more information from here: Is there a description of how __cmp__ works for dict objects in Python 2?. However it is not recommended to rely on this feature in your code.

Upvotes: 2

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