I/O means input and output

• file = open(filename) opens a file and returns it as a file object.
• file.read() – returns the specified number of bytes from the file. return string.
• file.readline() – returns a line of text of our current position.
• file.readlines() – returns a list containing each line in the file as a list item.
• file.seek(offset) - sets the file's current position at the offset.
• file.close() - opening too many file objects might fill up the memory for large programs. No matter how small your program is, keep a good habit of closing your file object!

file = open('myFile.txt') #取得一個file物件
print(file.read()) 
file.seek(0)
print(file.read(5))
print(file.read(5))
print(file.read(5))
print(file.readline())
print(file.readline()) 
file.close()
-----------------------------------
hello, how are you today?
I'm fine, thank you.
hello
, how
 are 
you today?
I'm fine, thank you.

file = open('myFile.txt')
while True:
    line = file.readline()
    if not line: # if line is empty dtring then end to read
        break
    else:
        print(line)
file.close()

encoding

在繁中windows系統中預設編碼是cp950(big 5)，則如果要打開一個utf-8的文件則要使用encoding的參數

file = open('myFile.txt', encoding='utf-8')

with

可讀性較高的寫法且會幫我們自動close

with open('myFile.txt') as my_file:
    all_content = my_file.read()
    print(all_content)
    
---------------------------------
hello, how are you today?

I'm fine, thank you.

with open('myFile.txt') as my_file:
    all_content = my_file.read().splitlines()
    for i in range(len(all_content)):
        print(all_content[i])
    
---------------------------------
hello, how are you today?
I'm fine, thank you.

with open('myFile.txt') as my_file:
    for line in my_file.readlines():
        print(line)
    
---------------------------------
hello, how are you today?

I'm fine, thank you.

with open('myFile.txt') as my_file:
    doc = my_file.readlines()
    doc = ''.join(doc).strip('\\n')
    
---------------------------------
hello, how are you today?
I'm fine, thank you.

• "r" - Read - Default value. Opens a file for reading, error if the file does not exist