87 lines
1.7 KiB
Markdown
87 lines
1.7 KiB
Markdown
### 读文件
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- 读取全部内容
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```python
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f = open("xxx.py")
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f.read()
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```
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- 读取指定多少个字符内容
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```python
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f = open("xxx.py")
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f.read(2)
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```
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- 按行读取：如果返回空就代表文件读完了
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```python
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>>> f = open("xxx.py")
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>>> f.readline()
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'This is the first line of the file.\n'
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>>> f.readline()
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'Second line of the file\n'
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>>> f.readline()
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''
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```
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- 读取所有行到list
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```python
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>>> f = open("module_support.py")
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>>> f.readlines()
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['#!/usr/bin/python3\n', '\n', 'def add(a, b):\n', ' return a + b\n', '\n', 'if __name__ == "__main__":\n', ' print("__main__")\n', 'else:\n', ' print(__name__)\n']
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>>>
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```
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- for循环读取每一行
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```python
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>>> f = open("module_support.py")
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>>> for line in f:
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... print(line, end = "")
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...
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#!/usr/bin/python3
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def add(a, b):
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return a + b
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if __name__ == "__main__":
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print("__main__")
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else:
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print(__name__)
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>>>
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```
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### 写文件
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```python
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f = open("module_support.py", "a") # 追加
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f = open("module_support.py", "w") # 文件不存在创建，存在就清空
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f.wtite("one line string")
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f.close()
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```
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### 文件操作cursor
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- f.tell() 显示当前cursor位置
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- f.seek(offset, from_what) 重新设置cursor位置
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- from_what 的值, 如果是 0 表示开头, 如果是 1 表示当前位置, 2 表示文件的结尾，例如：
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- seek(x, 0) ： 从起始位置即文件首行首字符开始移动 x 个字符
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- seek(x, 1) ： 表示从当前位置往后移动x个字符
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- seek(-x, 2)：表示从文件的结尾往前移动x个字符
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```python
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>>> f = open("module_support.py", "a")
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>>> f.tell()
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128
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>>> f = open("module_support.py", "a")
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>>> f.seek(10, 0)
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10
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>>>
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```
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