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pythonfunctionuser-defined-functions
TonyMorland
TonyMorland

Reputation: 103

Writing numerical lookup functions in python

In python, i would like to create several user-defined functions f(x) that are defined only at integer values x = i, where i ranges from 1 to several hundred. The functions themselves cannot be expressed as analytical or logical formulae but the values f(i) are known for all values i of the support range and so could be written as a table of pairs of values i, f(i).

Although i have written quite a few functions in python using def ..., I am still a python newbiwe, and i do not yet know how to efficiently code a function that must inherently use some form of numerical lookup table. I seek your assistance with an example of what would be appropriate code.

Upvotes: 0

Views: 1316

Answers (2)

Tom Dalton
Tom Dalton

Reputation: 6190

Use a dictionary e.g.

LOOKUP = {
    0: 100,
    1: 101,
    3: 102,
    9: 103,
}
def f(x):
    return LOOKUP[x]

Upvotes: 2

Daniel Roseman
Daniel Roseman

Reputation: 599788

You don't want a function for this. A mapping in Python is expressed via a dictionary.

mapping = {
    1: 300,
    3: 990,
    45: 267,
    # etc
}

result = mapping[value]

Upvotes: 2

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