py4_control structure

最新推荐文章于 2022-08-05 08:33:39 发布

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最新推荐文章于 2022-08-05 08:33:39 发布

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本文介绍了Python程序的控制结构，包括分支与循环结构，特别是简洁的条件判断和异常处理。异常处理部分讲解了try/except的用法，并强调了它与if/else的区别。此外，还概述了Python的随机库，列举了如seed、random、randint等基本随机函数的使用，强调了seed在重现实验中的重要性，并提及了其他如shuffle等实用函数。

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The Control Structure of Programs

Branch & Loop Structure
Compact type: $< c o m m a n d 1 >$ if $< c o n d i t i o n >$ else $< c o m m a n d 2 >$ , means if condition is judged true, do the command1, and if condition is judged false, do the command2.
Exception Handling: try/except combination, ATTENTION: try/except is different from if/else in Python, it’s NameError.

After the exception type is annotated, it only responds to THIS exception, and the name of the exception is same as the variable.
The high-level of using Exception Handling:
try:
$< c o m m a n d 1 >$
except:
$< c o m m a n d 2 >$
else:
$< c o m m a n d 3 >$
finally:
$< c o m m a n d 4 >$
The commands in Finally Struct must be executed, the commands in Else Struct will be executed when exception do not happen.

The overview of Random Library

Basic Random Function:
seed(a= None):Initialize the given-random number seed, default value is the time of system. e.g: random.seed(10) produce the sequence of the seed 10.
random(): generate a random decimal from 0.0 to 1.0.
WARNING: Using seed can get a accurate number of time, so we can playback the experiment we have done before, if don’t use the seed, the default value–system number–is a value accurate to the millisecond and it’s very difficult to recurrent.
randint(a, b): generate a random integer from a to b.
randrange(m, n, [k]): generate a random integer from m to n according to the step k, parameter k is alternate.
getrandbits(k): generate a random integer which is k bits long.
uniform(a, b): generate a random decimal from a to b, can reach the 16byte precision.

choice(seq): choose a element randomly from the sequence seq.
shuffle(seq): sort the elements in the sequence seq randomly, return the chaos-shuffled sequence.