试图写入到文件不会产生任何结果

Question

当试图用python读取文件时，它似乎只打印出一个空格，而不是“测试消息”。下面是我的代码：

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w+') as file:
        file.write(contents)
        print(file.read())

    
    
readAndWritetofile()

Answer 1

写入后，文件指针位于文件末尾。您可以返回开始或重新打开

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w+') as file:
        file.write(contents)
        file.seek(0)
        print(file.read())

readAndWritetofile()

或

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w') as file:
        file.write(contents)
        # exit the with closes the file
    with open("file.txt") as file:
        print(file.read())

readAndWritetofile()

Answer 2

您应该添加file.seek(0)。如果忘记了这一点，file.read()调用将尝试从文件末尾读取，并返回一个空字符串

当前，指针位于文件的末尾file.seek(0)将其移动到文件的开头

contents = "Test Message"

def readAndWritetofile():
    with open("file.txt", 'w+') as file:
        file.write(contents)
        file.seek(0)
        print(file.read())

readAndWritetofile()

Answer 3

你忘了

file.seek(0)

在6号线之前