--open of Python built-in functions

OPEN1, the Open function, which is used to process the file 2, open ("file name, mode (in what way), encode") A, basic open mode

　　　　　　　　

#1, read-only, Rf = open ("Ha.log","R")#2, write only, w,[file is not readable, the file does not exist, it is created; empty content]f = open ("Ha.log","W") F.write ("123") F.close ()#3, X, write-only mode "unreadable; not exist then create, present error"f = open ("Ha1.log","x") F.write ("456") F.close ()#4. Append mode "unreadable; not exist" create; append content only; "f = open ("Ha1.log","a") F.write ("666") F.close ()

B, Bytes open the way

#1, read-only, RBf = open ("Ha.log","RB") Data=F.read () f.close ( )Print(Type (data))#2. Write onlyf = open ("Ha.log","WB") f.write (bytes ("China", encoding="Utf-8") ) F.close ()

C, Difference:

# Normal Open # Normal Open has been internal Python operation, Direct is the UTF-8,RB way you need to convert # ===python internally converts 101010 = = to a string, using string manipulation # 010101 + =  python interpreter  + programmer # binary Open Way #RB Way open only get 2 binary code , you need to convert yourself into utf-8.

D, "+" 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"

1, r+

# R, append at the end, move the pointer to the last f = open ("ha.log","r+", encoding= " Utf-8 " # pointer is 0, start position #f.close ()

#从开始向后读
#写, append, pointer to last

2, w+,x+

#w+, clear the contents of the file, then write, you can read#first clear, then write to read, write, pointer to the lastf = open ("Ha.log","w+", encoding="Utf-8") F.write ("Wu") F.seek (0)#pointer pointing to 0data =F.read () f.close ( )Print(data) #x+ Basic Ibid. if file exists, then error

3. A +

A + A, open at the same time, the pointer has reached the end, the contents of the file can not be read # Write, will be appended, the pointer is put to the last f = open ("ha.log" ,"a+", encoding="utf-8"=  F.read () f.close ()print(data)

3, the operation function of the file

#===============================#F.tell () #获取指针的位置#f.seek (num) #调整指针的位置#===============================#Close file#Flush Force flush file Internal buffer#Read Reading file#ReadLine reading a line#pointer position in seek file#Tell to get the position of the pointer#truncate truncates data, leaving only the data before the pointer is specified#Write Read file

4, read the contents of each line

f = open ("ha.log","R", encoding="utf-8 " ) for in F:     print(line)  =#  F.readline, you can read the contents of all rows

5. With open

# When the with code block finishes executing, the file resource is automatically closed and freed internally. with open ("ha.log","R") as F:    F.read () # python inside will help you shut down without writing F.close

　

#open 2 files at a timeWith open ("Log1","R") as Boj1, open ("log2","R") as Obj2:Pass#open 2 files and transfer the dataWith open ("source File","R") as Obj1,open ("New File","W") as Obj2: forLineinchObj1:obj2.write (line)#Open a source file while the content is written in a new file

6. Lambda expression

# Lambda can replace a simple function def F1 ():     return 123Lambdadef  F3 (A1,A2):     return A1 +  Lambda a1,a2:a1+=print=print(R2)

　　　　

--open of Python built-in functions