1、open():

Python中的内置函数open会打开一个文件，并且返回一个文件对象。

尝试一：
# Python的文件操作
f = open(“12345.txt”, “r”)
print(f)

结果：
F:\PycharmWorkSpace\菜鸟教程，Python实例\venv\Scripts\python.exe F:/Pycharm_WorkSpace/菜鸟教程，Python实例/13文件IO.py
Traceback (most recent call last):
File “F:\PycharmWorkSpace\菜鸟教程，Python实例\13文件IO.py”, line 2, in
f = open(“12345.txt”, “r”)
FileNotFoundError: [Errno 2] No such file or directory: ‘12345.txt’

Process finished with exit code 1

思考：
知道了，Python打开的文件需要创建在项目里：

结果：
F:\PycharmWorkSpace\菜鸟教程，Python实例\venv\Scripts\python.exe F:/Pycharm_WorkSpace/菜鸟教程，Python实例/13文件IO.py
<_io.TextIOWrapper name='1234' mode='r' encoding='cp936'>

Process finished with exit code 0

2、创建文本文件：

file = open(“12345”, “w”)
file.write(“Hello!”)
file.close()

会在项目里创建一个文件，并写入内容：

3、读取文本文件：

先创建一个文本文件：
file = open(“ReadTheFile”, “w”)
file.write(“Hello!”)
file.write(“My name is Zhang Yupei”)
file.write(“I am 23 years old this year.”)
file.write(“I am a girl.”)
file.close()
查看结果：

啊这，不换行啊。修改代码，重新生成：

1）读所有内容，read()

f = open(“ReadTheFile”, “r”)
print(f.read())
结果：
F:\PycharmWorkSpace\菜鸟教程，Python实例\venv\Scripts\python.exe F:/Pycharm_WorkSpace/菜鸟教程，Python实例/13文件IO.py
Hello!
My name is Zhang Yupei
I am 23 years old this year.
I am a girl.

2）读部分内容，read(n)

f = open(“ReadTheFile”, “r”)
print(f.read(15))
结果：
F:\PycharmWorkSpace\菜鸟教程，Python实例\venv\Scripts\python.exe F:/Pycharm_WorkSpace/菜鸟教程，Python实例/13文件IO.py
Hello!
My name

3）一行一行读，readline()

若只使用一次，则只读取第一行：
f = open(“ReadTheFile”, “r”)
print(f.readline())

结果：
Hello!My name is Zhang Yupei

再一次：
f = open(“ReadTheFile”, “r”)
print(f.readline())
print(f.readline())
print(f.readline())

结果：
Hello!My name is Zhang Yupei

I am 23 years old this year.

I am a girl.

【注】：每一行输出之后，都会再空一行。

4）返回每行数据，readlines()

f = open(“ReadTheFile”, “r”)
print(f.readlines())

结果：
[‘Hello!\n’, ‘My name is Zhang Yupei\n’, ‘I am 23 years old this year.\n’, ‘I am a girl.’]

5)循环显示文件对象

f = open(“ReadTheFile”, “r”)
for line in f:
print(line)
f.close()

结果：
Hello!

My name is Zhang Yupei

I am 23 years old this year.

I am a girl.

Process finished with exit code 0