Ch5 I/O with Files in Python

✨與文件同一個資料夾叫出

For txt

• file = open(filename) #opens a file and returns as a file object
• file.read() #return the specified number of bytes from the file 全篇輸出 ‘string’
• file.readline() #return a line of text of our current position 輸出 ‘list’(a list of strings)
• file.readlines #return a list of containing each line in the file as a list item 全篇輸出 ‘list’(a list of strings) 增加佔據RAM
• file.seek(offest) #set the file’s current position at the offset 讀取處從指定處開始 (0)指向起點
• file.close() #不執行不會怎樣，但打開太多檔案會佔據太多RAM => 不論檔案大小，最好都要close

file = open('myfile.txt')
print(file)
#<_io.TextIOWrapper name='myfile.txt' mode='r' encoding='cp1252'>
print(file.read()) #輸出所有內容
file.seek(0)
print(file.read(5)) #seek 會變
print(file.read(5)) #接續前面讀取的地方
print(file.readlines()) #接續前面讀取的地方
for line in file.readlines():
    print(line)

while True:
	line = file.readline()
	if line == '': #也可以打 if not line => 如果沒有讀到東西
		break
	else:
		print(line)

(Bonus) Encoding

• character encoding is the process of assigning numbers to graphical characters ⇒ a = 20
• common encoding: utf-8 (html常用), cp950(中日文電腦), ASCII
• open() based on default, Chinese Windows ⇒ cp950 if want to open utf-8 file, must type: open(filename, encoding = ‘utf-8’)

With Statement and Open() Function

• cleaner and readable, also will automatically close the file
• 設定開啟模式:

1. r : read (default) #open file for reading, error if file doesn’t exist
2. a : append #open for appending, create the file if it doesn’t exist #文件變得unreadable, 不能用read()
3. w : write #open for writing, create the file if it doesn’t exist
4. x : create #return an error if file exists

with open('myfile.txt', mode = 'r') as myfile:
    all_content = myfile.read()
    print(all_content)

with open('myfile.txt', mode = 'a') as myfile:
    myfile.write('Hi! It is a great day')
#新增行
with open('myfile.txt', mode = 'w') as myfile:
    myfile.write('Hi! It is a great day.\\n Want to go out?')
#覆蓋、複寫行(文件中只剩這一行)

Deleting Files and Folders