Liao Xue python excerpt 2

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1, in the computer memory, the unified use of Unicode encoding, when the need to save to the hard disk or need to transfer, the conversion to UTF-8 encoding.

When editing with Notepad, the UTF-8 characters read from the file are converted to Unicode characters into memory, and when the edits are complete, the conversion of Unicode to UTF-8 is saved to the file.

2, for the encoding of a single character, Python provides a ord() function to get the integer representation of the character, the chr() function converts the encoding to the corresponding character:

3, because the string type of Python is str , in memory in Unicode, a character corresponding to a number of bytes. If you want to transfer on a network, or save to disk, you need to turn it str into bytes bytes .

4, % the operator is used to format the string. Inside the string, the representation is replaced by a string, which %s %d is replaced with an integer, there are several %? placeholders, followed by a number of variables or values, the order to correspond well.   If there is only one %? , the parentheses can be saved. ' Hello%s,you has%s money ' (' Mike ', 1000) error ' Hello%s,you has%s money '% (' Mike ', 1000) correct!

5, escaped, used %% to denote a%。

' %2d-%02d ' % (3, 1)'  3-01'%.2f' % 3.1415926'  3.14'

6, List if you want to take the last element, in addition to the calculation of the index location, you can also use -1 the index to get the last element directly

7. The data type of the elements in the list can also be different; The list element can also be another list.

8, another ordered list called tuples: tuple. Tuple and list are very similar, but a tuple cannot be modified once initialized

classmates = (‘Michael‘, ‘Bob‘, ‘Tracy‘)

9. What is the meaning of immutable tuple? Because the tuple is immutable, the code is more secure. If possible, you can use a tuple instead of a list as much as possible.

Each element of a tuple, pointing to never change. That is, pointing ‘a‘ , cannot be changed to point ‘b‘ , point to a list, can not be changed to point to other objects, but the list itself is variable!

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Liao Xue python excerpt 2