Functions of Python

1 "Function:
1> definitions, keywords and calls:

The return value of the 2> function:

General parameters of the 3> function:

Default parameters for the 4> function: The default parameter must be placed at the end;

　　　　　　

Parameters can be specified:

5> Dynamic Parameters:
*: Converts the passed-in parameter to a tuple;

* *: Converts the passed in parameter to a dictionary:

　　　　　　　　

*,**: You can process incoming parameters into tuples and dictionaries at the same time, the parameters must first specify *, then specify * *;

　　　　　　　　　

The parameter variables passed in represent tuples or dictionaries:

2. Format strings using dynamic parameters:

　　　　

3 lambda expression: simple representation of simple function;

　　　　

4 "Python built-in functions:
Common built-in functions:

1>abs (): absolute value;
2>all (): The element that will loop input, only if all elements are true will output true, otherwise false;

　　　　

3>any (): As long as one of them is true, it is true;

4>ascii (): Equivalent to int.__repr__, returns the ASCII code of the input value;
5>bin (): The input parameters can be converted into binary digits;

6>bytearray (): can convert input elements into byte arrays, one kanji three bytes; (Not supported in 2)

p = ByteArray (' Chei Huiwei ', encoding=' Utf-8 ')
　　　　　　　　Print (p)

7>callable (): The variable is followed by parentheses whether it is executable;

　　　　　　　　

8>CHR (): converts ASCII to characters;
Ord (): Converts characters into ASCII code;

　　　　　　　　

9>classmethod (): Object-oriented use;
10>compile (): A string can be compiled into Python code;
11>delattr (): used when reflecting;
12>enumerate (): Adds a column of self-increment elements to the loop output;

13>eval ():
>>> eval ("6*8")
48
>>>
14>filter (): Filters the elements in the sequence and finally gets the sequence that matches the conditions;

15> map (): Iterates through the sequence, operates on each element of the sequence, and finally acquires a new sequence;

17>frozenset (): cannot be added with the modified collection;
18>globals (): all currently available variables;
19>hex (): converted to 16 binary;
20>max (): Take the maximum value;
Max (11,22,33,44)
21>oct (): converted to octal;
22>range ():

　　　　　　　　

23>reversed (): invert;
24>round (): rounds the input numbers;
25>zip (): Re-group two lists, tuples or dictionaries;

26>open (): Used to manipulate files;
R: read-only mode;
W: write-only mode; (unreadable, not present, created, delete content exists)
A: Append mode (readable, non-existent, create, only append content if present)
+: Indicates that you can read and write files simultaneously:
R+: Can read and write files, (readable, writable, can be appended)
w+: Write and read;
A +: with A;
U: indicates that \ r \ n can be automatically converted to \ n (in conjunction with R or r+ mode) when reading
Ru
R+u:
B: Represents the processing of binary files;
Rb
Wb
Ab

Read two bytes:

　　　　　　　　

Read Chinese characters, a Chinese character three bytes (3 in the character read, a Chinese character and a letter is a character):

27>tell (): The position where the pointer can be output;

　　　　　　

28>seek (): You can specify where you want the pointer to jump, specifying the current pointer position;

29>read (): Specifies the number of characters to read;
30>truncate (): Specify the current pointer position, and then modify the original file so that the original file only the current pointer before the Rrong capacity (test.log:123456);

　　　　　　　　

31>json.loads (): A dictionary-like string can be converted to a dictionary (3 can be, 2 does not);

　　　　　　　　

　　　　　

Functions of Python