The role of Python assert

One, the role of Python assert:

According to the official Python document (Https://docs.python.org/3/reference/simple_stmts.html#assert), "Assert statements is a convenient The-to-insert debugging assertions into a program.

Second, the general usage is:

Assert condition

Used to let the program test this condition, if condition is false, then raise a assertionerror out. Logically equivalent to:

If not condition:    raise Assertionerror ()

For example, the following examples:

>>> assert 1==1>>> assert 1==0traceback (most recent call last):  File "<pyshell#1>", line 1, I n <module>    assert 1==0assertionerror>>> assert true>>> assert Falsetraceback (most recent Call last):  File ' <pyshell#3> ', line 1, in <module>    assert falseassertionerror>>> assert 3 <2traceback (most recent):  File "<pyshell#4>", line 1, in <module>    assert 3< 2AssertionError

Iii. How to add an exception parameter for an ASSERT assertion statement

The exception argument to assert is to add string information after the assertion expression to explain the assertion and better know where the problem is. The format is as follows:

assert expression [, arguments]
assert expression [, parameter]

For example, the following examples:

>>> assert len (lists) >=5, ' list element number less than 5 '

Traceback (most recent):
File "d:/data/python/helloworld/helloworld.py", line 1, <module>
Assert 2>=5, ' list element number less than 5 '
Assertionerror: Number of list elements is less than 5

>>> assert 2==1, ' 2 not equal to 1 '

Traceback (most recent):
File "d:/data/python/helloworld/helloworld.py", line 1, <module>
Assert 2==1, ' 2 not equal to 1 '
Assertionerror:2 Not equal to 1

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Reference Links:

Https://www.cnblogs.com/liuchunxiao83/p/5298016.html

Https://www.cnblogs.com/cedrelaliu/p/5948567.html

The role of Python assert