Python的IO（输入/输出）操作是编程中非常基础且重要的部分，它允许程序与外部世界进行交互。本文将详细介绍Python中的文件读写操作、标准输入输出以及相关的最佳实践。
一、文件读写操作
1. 打开和关闭文件
在Python中，使用open()函数打开文件，使用close()方法关闭文件。
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file = open('example.txt', 'r')
content = file.read()
print(content)
file.close()
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2. 文件打开模式
| 模式 |
描述 |
| r |
只读模式（默认） |
| w |
写入模式，会覆盖现有文件 |
| a |
追加模式，在文件末尾添加内容 |
| x |
独占创建模式，如果文件已存在则报错 |
| b |
二进制模式 |
| t |
文本模式（默认） |
| + |
读写模式 |
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with open('image.jpg', 'rb') as f:
data = f.read()
with open('example.txt', 'r+') as f:
content = f.read()
f.write('Additional content')
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3. 使用with语句
with语句是处理文件的推荐方式，它会自动管理文件的关闭，即使出现异常也能保证文件正确关闭。
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with open('example.txt', 'r') as file:
content = file.read()
print(content)
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4. 读取文件内容
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with open('example.txt', 'r') as f:
content = f.read()
print(content)
with open('example.txt', 'r') as f:
for line in f:
print(line.strip())
with open('example.txt', 'r') as f:
content = f.read(100)
print(content)
with open('example.txt', 'r') as f:
lines = f.readlines()
print(lines)
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5. 写入文件内容
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with open('example.txt', 'w') as f:
f.write('Hello, world!\n')
f.write('This is a test.\n')
with open('example.txt', 'a') as f:
f.write('Additional line.\n')
lines = ['Line 1\n', 'Line 2\n', 'Line 3\n']
with open('example.txt', 'w') as f:
f.writelines(lines)
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二、标准输入输出
1. 标准输出（print）
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print('Hello, world!')
print('Hello', 'world', '!')
print('Hello', 'world', sep=', ')
print('Hello', end=' ')
print('world')
name = 'Alice'
age = 25
print(f'Name: {name}, Age: {age}')
print('Name: {}, Age: {}'.format(name, age))
print('Name: %s, Age: %d' % (name, age))
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name = input('Enter your name: ')
print(f'Hello, {name}!')
age = int(input('Enter your age: '))
print(f'You are {age} years old.')
print('Enter multiple lines (press Ctrl+D to end):')
lines = []
while True:
try:
line = input()
lines.append(line)
except EOFError:
break
print('You entered:')
for line in lines:
print(line)
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三、二进制文件操作
1. 读取二进制文件
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with open('image.jpg', 'rb') as f:
data = f.read()
print(f'File size: {len(data)} bytes')
with open('image.jpg', 'rb') as f:
header = f.read(10)
print(f'Header: {header}')
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2. 写入二进制文件
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data = b'Hello, binary world!'
with open('binary.bin', 'wb') as f:
f.write(data)
with open('source.jpg', 'rb') as src:
with open('destination.jpg', 'wb') as dst:
while True:
chunk = src.read(1024)
if not chunk:
break
dst.write(chunk)
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四、文件位置操作
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with open('example.txt', 'r+') as f:
print(f'Current position: {f.tell()}')
content = f.read(10)
print(f'Read: {content}')
print(f'Position after read: {f.tell()}')
f.seek(0)
print(f'Position after seek(0): {f.tell()}')
f.seek(0, 2)
print(f'Position at end: {f.tell()}')
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五、异常处理
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try:
with open('non_existent_file.txt', 'r') as f:
content = f.read()
except FileNotFoundError:
print('Error: File not found')
except PermissionError:
print('Error: Permission denied')
except Exception as e:
print(f'Error: {e}')
try:
with open('protected_file.txt', 'w') as f:
f.write('Test content')
except Exception as e:
print(f'Error writing file: {e}')
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六、高级文件操作
1. 文件路径操作
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| import os
import pathlib
print(f'Current directory: {os.getcwd()}')
file_path = os.path.join('data', 'example.txt')
print(f'File path: {file_path}')
print(f'File exists: {os.path.exists(file_path)}')
path = pathlib.Path('data') / 'example.txt'
print(f'Path: {path}')
print(f'Path exists: {path.exists()}')
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2. 文件信息
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| import os
import stat
file_path = 'example.txt'
if os.path.exists(file_path):
print(f'File size: {os.path.getsize(file_path)} bytes')
print(f'Last modified: {os.path.getmtime(file_path)}')
print(f'Is file: {os.path.isfile(file_path)}')
print(f'Is directory: {os.path.isdir(file_path)}')
from pathlib import Path
path = Path('example.txt')
if path.exists():
print(f'File size: {path.stat().st_size} bytes')
print(f'Last modified: {path.stat().st_mtime}')
print(f'Is file: {path.is_file()}')
print(f'Is directory: {path.is_dir()}')
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七、综合示例
1. 文本文件处理
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"""
文本文件处理示例
"""
def read_file(file_path):
"""读取文件内容"""
try:
with open(file_path, 'r', encoding='utf-8') as f:
return f.read()
except Exception as e:
print(f'Error reading file: {e}')
return None
def write_file(file_path, content):
"""写入文件内容"""
try:
with open(file_path, 'w', encoding='utf-8') as f:
f.write(content)
return True
except Exception as e:
print(f'Error writing file: {e}')
return False
def append_file(file_path, content):
"""追加文件内容"""
try:
with open(file_path, 'a', encoding='utf-8') as f:
f.write(content)
return True
except Exception as e:
print(f'Error appending file: {e}')
return False
def count_lines(file_path):
"""统计文件行数"""
try:
with open(file_path, 'r', encoding='utf-8') as f:
return sum(1 for line in f)
except Exception as e:
print(f'Error counting lines: {e}')
return 0
def main():
test_file = 'test.txt'
content = 'Hello, world!\nThis is a test.\nPython IO operations.'
if write_file(test_file, content):
print(f'File {test_file} created successfully.')
file_content = read_file(test_file)
if file_content:
print(f'File content:\n{file_content}')
append_content = '\nAdditional line.'
if append_file(test_file, append_content):
print('Content appended successfully.')
file_content = read_file(test_file)
if file_content:
print(f'Updated file content:\n{file_content}')
line_count = count_lines(test_file)
print(f'Number of lines: {line_count}')
if __name__ == '__main__':
main()
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2. 二进制文件处理
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"""
二进制文件处理示例
"""
def copy_file(src_path, dst_path):
"""复制文件"""
try:
with open(src_path, 'rb') as src:
with open(dst_path, 'wb') as dst:
while True:
chunk = src.read(1024 * 1024)
if not chunk:
break
dst.write(chunk)
print(f'File copied from {src_path} to {dst_path}')
return True
except Exception as e:
print(f'Error copying file: {e}')
return False
def read_binary_file(file_path):
"""读取二进制文件"""
try:
with open(file_path, 'rb') as f:
return f.read()
except Exception as e:
print(f'Error reading binary file: {e}')
return None
def main():
test_file = 'test.bin'
binary_data = b'Hello, binary world!\x00\x01\x02\x03'
with open(test_file, 'wb') as f:
f.write(binary_data)
print(f'Binary file {test_file} created.')
data = read_binary_file(test_file)
if data:
print(f'Read {len(data)} bytes: {data}')
copy_file(test_file, 'test_copy.bin')
if __name__ == '__main__':
main()
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八、最佳实践
- 始终使用with语句：确保文件正确关闭，避免资源泄漏
- 指定编码：在处理文本文件时，明确指定编码（如utf-8）
- 异常处理：捕获并处理可能的文件操作异常
- 分块处理：对于大文件，使用分块读取和写入
- 使用pathlib：对于路径操作，推荐使用pathlib模块
- 文件权限：确保有适当的文件读写权限
- 文件路径：使用相对路径或绝对路径时要注意跨平台兼容性
- 二进制模式：处理非文本文件时使用二进制模式
九、总结
Python的IO操作提供了强大而灵活的文件处理能力，无论是文本文件还是二进制文件，都可以通过简洁的语法进行操作。通过本文的介绍，你应该已经掌握了Python中文件读写、标准输入输出以及相关的高级操作。在实际项目中，合理使用这些IO操作可以帮助你更有效地处理数据和与外部世界交互。
