Python Programming--File manipulation

Classification

1. Text files

Stores regular strings, consisting of several lines of text, with each line ending with a newline character ' \ n '

2. binary files

Store objects in byte strings, common graphics images, executables, database files, Office documents, and more

1 #Create a file2>>FW = open ('Sample.txt','w+', encoding='Utf-8')3>>s ='text read \ n sample.txt w+\n'4>>Fw.write (s)5>>fw.close ()6 #View Sample.txt7 Text Read mode8Sample.txt w+9 Ten #suggested form, keyword with to manage resources automatically One>>s ='text read \ n sample.txt w+\n' A>>with Open ('Sample.txt','w+', encoding='Utf-8') as FW: ->>Fw.write (s) - #determine if the file object is closed the>>fw.colsed - True -  - #Add File Contents +>>s ='hello\n' ->>with Open ('Sample.txt','A +', encoding='Utf-8') as FA: +>>Fa.write (s) A Text Read mode atSample.txt w+ - Hello -  - #Read File contents - #read a row ->>fread = open ('Sample.txt','R', encoding='Utf-8') in>>Fread.readline () - 'text Read method \ n' to>>Fread.readline () + 'sample.txt w+\n' ->>Fread.readline () the 'hello\n' *  $ #read all rows at oncePanax Notoginseng>>fread = open ('Sample.txt','R', encoding='Utf-8') ->>Fread.readlines () the['text Read method \ n','sample.txt w+\n','hello\n'] +  A #read fixed number of characters the>>fread = open ('Sample.txt','R', encoding='Utf-8') +>>fread.read (4) - 'Text Read'
>>fread.close ()

You can use Dir () to view methods associated with an object, using Help () to view the usage of the method

1 >>fread = open ('sample.txt','r', encoding= ' Utf-8 ' )2 >>fread.colse ()3 >>dir (fread)4 # view read () function usage 5 >>help (fread.read)

Serialization of files

Serialization is the process of converting in-memory data into binary form without losing data types.

1. Using the Pickle module

Pickle is a common and fast binary file serialization module

1 #using pickle Dump to write binary files in sequence2 ImportPickle3f = open ('Sample_pickle.dat','WB')4 5Alist = [[2,3,4],[6,7,8]]6Aset = {'a','b','C'}7Atuple = ( -5,-3,-1)8Astr ='Beijing welcomes you, welcome!'9adic = {'name':'Jin','Sex': None}Ten Try: One pickle.dump (alist,f) A pickle.dump (aset,f) - pickle.dump (atuple,f) - pickle.dump (astr,f) the pickle.dump (adic,f) - except: -     Print('Write Error') - finally: + f.close () -  + #using pickle load to read binary files in turn AFR = Open ('Sample_pickle.dat','RB') at Try: -x=Pickle.load (FR) -     Print(x) -x=Pickle.load (FR) -     Print(x) -x=Pickle.load (FR) in     Print(x) -x=Pickle.load (FR) to     Print(x) +x=Pickle.load (FR) -     Print(x) the except: *     Print('Read Error') $ finally:Panax NotoginsengFr.close ()

2. Using a struct module

1 Importstruct2 ImportBinascii3  4Values = (1, b'Good', 1.22)#string must be a byte stream type5s = struct. Struct ('I4SF')6Packed_data = S.pack (*values)#Sequence Unpacking7Unpacked_data =S.unpack (packed_data)8   9 Print('Original values:', values)Ten Print('Format String:', S.format) One Print('Uses:', S.size,'bytes') A Print('Packed Value:', Binascii.hexlify (packed_data)) - Print('unpacked Type:', type (unpacked_data),'Value:', Unpacked_data) -  the Out : -Original values: (1, b'Good', 1.22) -Format string:b'I4SF' -Uses:12bytes +Packed value:b'01000000676f6f64f6289c3f' -Unpacked Type: <class 'tuple'> Value: (1, b'Good', 1.2200000286102295)

Python Programming--File manipulation