Python entry _ introduction to logical judgment and operators, and introduction to python

Python entry _ introduction to logical judgment and operators, and introduction to python

This is the 6th article on Python, which mainly introduces logical judgment and operators.

(1)

Logical judgment:

To implement a complex functional program, logical judgment is essential. The most basic criterion for logical judgment: boolean type.

The boolean type has only two values: True and False, which correspond to 1 and 0 in Python.

Enter the following code in Pycharm. After running the command, the feedback is True or False.

print(1 > 2)print('m' in 'member')print(7 >= 7)print(3 != 3)

Here, the expression that can return a Boolean value is called a Boolean expression. There are many boolean expressions, which are described below.

(2)

1. Comparison operators:

If the comparison is True, True is returned. If the comparison is not True, False is returned.

Common comparison operators are as follows:

In addition to comparing simple two values, comparison operators also support relatively complex comparisons.

(1) Multi-condition comparison:

You can assign a value to variable a and then compare multiple conditions.

 a = 3 print(1 < a < 5)

(2) Comparison of variables:

Assign values to variables a and B for comparison.

a = 3b = 3print(a != b)s1 = 'duwangdan's2 = 'DuWangDan'print(s1 == s2)

(3) Comparison of function results:

Print (abs (-1)> len ('duwagndanc') # abs (): returns the absolute value of the input parameter.

There are some minor issues to be aware of in comparison operations:

Different types of objects cannot be compared using ">, >=, <, <=", but can use "= ,! =.

 print(21 == len('duwangdan'))

As stated at the beginning of the article, True corresponds to 1, and False corresponds to 0. In the following example, False + True is actually equivalent to 0 + 1:

print(False + True > False + False)

2. member operators:

The keyword of the member operator is "in" to determine whether an element is in a list. After running the following program, you can get feedback.

A = 1 B = 'beotiul' album = [1, 'beotiully ', False, 7] # create a list named album print (a in album) print (B in album

When album = [], the list is empty.

If you want to add content to album, you can use the append method. The added content is displayed at the end of the list.

Album = [1, 'betifully ', False, 7] album. append ('wow') # Use the append () method to add content print (album) to album)

3. Identity operators:

The identity operator is used to compare whether two objects are the same object, while "=" in the previous comparison operator is used to compare whether the values of the two objects are equal.

Identity operators are mainly determined by "is, is not.

a = 'duwangdan'b = 'duwangdan'print(a is b)print(a is not b)

4. boolean operator:

There are three boolean operators in Python: and, or, and not.

In the following example, the returned results are: False, True, and True.

print(1 > 2 and 1 > 0)print(1 > 2 or 1 > 0)print(not False)

The main content of this article is here, and we will introduce conditional control in the future.

Operating Environment: Python version, 3.6; PyCharm version, 2016.2; Computer: Mac

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