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.
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.
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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