# Python檔案讀寫
###### tags: `基本語法`

## with open as 語句
在Python中，可以使用`with open("file_path","open_mode") as varialbe`語句讀/寫基本檔案。

其中有以下常見的檔案開啟模式：

| 模式 |功能|特性|
| -------- | -------- | -------- |
|"w"|只能寫入|指標位於檔頭|
|"r"|只能讀取|指標位於檔頭|
|"a"|只能寫入(填加)|指標位於檔位|

## 基本的寫入語法

1. `.write(str)` 將字串寫入。
2. `.writelines()` 將如可迭代的字串資料寫入。

程式範例

with open('1.txt', 'w') as file:
    text = "hello world\n"
    texts = ["how ", "are ", "you?"]

    file.write(text)
    file.writelines(texts)

1.txt

hello world
how are you?

## 基本的讀取語法
1. `.read(int|None)` 返回讀取的字串，如果沒有傳入參數就讀取整個檔案，否則則讀取指定的字元數。
2. `.readline()` 讀取第一行
3. `.readlines()`讀取所有行數，回傳成一個串列

### `read()`程式範列

1.txt
hello world
how are you?

with open('1.txt') as file:
    all_content = file.read()
    print(all_content)

output:
hello world
how are you?

### `readline()`程式範列

with open('1.txt') as file:
    line = file.readline()
    print(line)

output:
hello world

### `readlines()`程式範列

with open('1.txt') as file:
    lines = file.readlines()
    print(lines)

output:
['helloworld\n', 'how are you?']