修改txt内容

def updateFile(file,old_str,new_str):
    file_data = ""
    with open(file, "r") as f:
        for line in f:
            line = line.replace(old_str,new_str)
            file_data += line
    with open(file,"w") as f:
        f.write(file_data)
updateFile(r'C:\Users\mage\Desktop\新建文本文档.txt','I am very happy.','but I am unhappy')

修改前，注意，只能修改非中文的内容

 修改后

注意：这段代码若file不存在，则会自动创建一个

with open(file,"w") as f:
        f.write(file_data)