The way of Python ——— chapter II: Functions

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First, the function one, the definition function

Def f1 (): #定义函数

Asdf

1.def #关键字, creating functions

2.F1 #函数名

3. ()

4.asdf.. #函数体 (Code executed)

5. Return value

F1 () #执行函数

The definition of a function has the following main points:

• def: A keyword that represents a function
• Function name: the names of functions, which are called later by function name
• function Body: The function of a series of logical calculations, such as: Send mail, etc...
• Parameters: Providing data for the function body
• Return value: Once the function has finished executing, it can return data to the caller.

Second, the parameters

1. General parameters: The actual parameters are assigned to formal parameters in strict order

2. Default parameters: Must be placed at the end of the parameter list

3. Specify parameters: give the actual parameter assignment to the prescribed formal parameters

4. Dynamic Parameters:

*: The default will be stored in the parameters, all placed in the tuple, F1 (*[11,22,33,44])

* *: Default to pass in the parameters, all placed in the dictionary F1 (**{"K1": "V1", "K2": "V2"})

5. Universal Parameters: *args,**kargs

6. The value of the parameter is transmitted by reference

Third, global variables

1. All scopes are readable

2. Re-assignment of global variables requires global

3. If the variable is a list, dictionary, you can modify it, but you cannot reassign the value

4. Define global variables to all capitals (unspoken rules)

Two or three-dollar operation (Trinocular operation)

#对if_else的简写

　　　　　　#如果 1==1 established
#name = "You"
#否则
#name = "SB"
Name = = "You" if 1 = = 1 else "SB"

Third, lambda expression

#对函数的简写, can only be done on one line

　　　　F2 = Lambda a1:a1 +

　　　　Name of #f2 function

#a1 parameters

#默认返回执行之后的结果

iv. operation of the file

Open function: This function is used to process the file

First, open the file

The mode of opening the file is:

R, read-only mode "default"

W, write-only mode "unreadable; not exist" created; empty content;

X, write-only mode "unreadable; not present, create, present error"

A, append mode "readable; not present, create; append content only;"

"+" means you can read and write a file at the same time

r+, read and write "readable, writable"

w+, write "readable, writable"

x+, write "readable, writable"

A +, write "readable, writable"

"B" means to operate in bytes

RB or R+b

WB or W+b

XB or W+b

AB or A+b

Note: When opened in B, the content read is byte type, and the byte type is also required for writing

Second, the operation

Read () #无参数, read all; Parameters: (b: by Byte; no B: by character)
Tell () #获取当前指针位置 (bytes)
Seek () #指针跳转到指定位置 (bytes)
Write () #写数据, B: by Byte; no B: by character
Fileno () #文件描述符
Flush () #强刷到硬盘
ReadLine () #仅读取一行
Truncate () #截断, empty everything behind the pointer
For loop file object for Line in f:
print (line)

　

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The way of Python ——— chapter II: Functions