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5.5. Random numbers¶
If you give most computer programs the same input multiple times, they will always produce exactly the same output. Programs like this are said to be deterministic. Determinism is usually a good thing, since we expect the same calculation to yield the same result. For some applications, though, we want the computer to be unpredictable. Games are an obvious example, but there are more.
Making a program truly nondeterministic turns out to be no easy task, but there are ways to make programs at least seem nondeterministic. One way is to use algorithms that generate pseudorandom numbers. Pseudorandom numbers are not truly random because they are generated by a deterministic computation, but just by looking at the numbers it is all but impossible to distinguish them from a truly random set.
random module provides functions that generate
pseudorandom numbers (which I will simply call “random” from here on).
random returns a random float between 0.0 and
1.0 (including 0.0 but not 1.0). Each time you call
you get the next number in a long series. To see a sample, run this
This program produces the following list of 10 random numbers between 0.0 and up to but not including 1.0. Notice how the numbers you ran above are different than the ones below, which were generated earlier.
0.11132867921152356 0.5950949227890241 0.04820265884996877 0.841003109276478 0.997914947094958 0.04842330803368111 0.7416295948208405 0.510535245390327 0.27447040171978143 0.028511805472785867
Run the program more than once and see what numbers you get.
random function is only one of many functions that
handle random numbers. The function
randint takes the
high, and returns an
high (including both).
To choose an element from a sequence at random, you can use
random module also provides functions to generate
random values from continuous distributions including Gaussian,
exponential, gamma, and a few more.
Construct a block of code that correctly generates a random integer between 1 and 100 (inclusive), then prints it out. Hint: there are two code blocks that are not used.
Construct a block of code that correctly generates a random number from the list called “nums”, then prints it out. Hint: there are four code blocks that are not used.