Function to read and write file operations of python

Function to read the file

#1: read()函数读取文件中的所有内容。
data_file = "E:\python_linux\s004_string_judge.py"
file_obj = open(data_file,'r',encoding = 'utf-8')
print("read()函数读取整个文件内容；\n",file_obj.read(),end='\n')
'''当运用了read()类函数，文件指针会有偏移，偏移为读取到的最后一个字符。
   若要重新读取，则要把文件指针放回到文件开头。用seek()方法'''
file_obj.seek(0)

result

#--------前缀------------#
s_pro = s.startswith('wan')
print('字符串s的前缀可以是wan:',s_pro)

#--------后缀-----------#
s_end = s.endswith('ya !')
print('字符串s的后缀可以是ya ！',s_end)

#-------实例:筛选某个目录下的.py文件------------#
file_list = ['a.py', 'b.py', 'c.txt', 'd.py']
py_file = [file for file in file_list if file.endswith('.py')]
print('当前路径下的python文件:',py_file)

#2: readline()方法读取文件中一行内容。适合用for循环迭代。
print('readline()方法读取文件一行内容：\n',file_obj.readline(),end='\n')
file_obj.seek(0)
for file_line in file_obj:
    print('++++++++'+file_obj.readline(),end='\n')
file_obj.seek(0)

result

readline()方法读取文件一行内容：
 #------------字符串前缀和后缀的判别方式--------#

++++++++

++++++++#--------前缀------------#

++++++++print('字符串s的前缀可以是wan:',s_pro)

++++++++#--------后缀-----------#

++++++++print('字符串s的后缀可以是ya ！',s_end)

++++++++#-------实例:筛选某个目录下的.py文件------------#

++++++++py_file = [file for file in file_list if file.endswith('.py')]

++++++++

#3: readlines()方法读取整个文件，存为一个列表。
print('readlines()方法：\n',file_obj.readlines(),end = '\n')
file_obj.close()

result

readlines()方法：
 ['#------------字符串前缀和后缀的判别方式--------#\n', '\n', 's = "wan quan he ni hao ya !"\n', '#--------前缀------------#\n', "s_pro = s.startswith('wan')\n", "print('字符串s的前缀可以是wan:',s_pro)\n", '\n', '#--------后缀-----------#\n', "s_end = s.endswith('ya !')\n", "print('字符串s的后缀可以是ya ！',s_end)\n", '\n', '#-------实例:筛选某个目录下的.py文件------------#\n', "file_list = ['a.py', 'b.py', 'c.txt', 'd.py']\n", "py_file = [file for file in file_list if file.endswith('.py')]\n", "print('当前路径下的python文件:',py_file)\n"]
>>> 

File write function

1:write:写一个字符串到文件中，并返回写入的字符个数。
write_file = "E:\python_linux\write_function.txt"
write_contant = ["它是一只狗！",'这是只猫。','它在睡觉。']
with open(write_file,'w') as w_file:
    w_file.write('你是一个好人；')
#2:write:将一个列表写入到文本中。
    w_file.writelines(write_contant)
# 注意在写入文件的过程中，也是有文件指针偏移的。
#是通过关闭文件回到初始位置的，也可以用seek

#3:利用print()函数将字符串写入到文本中。
with open('E:\python_linux\write_function.txt','w') as pw_file:
    print(1,2,'hello world!',sep=",",file=pw_file)
    print("这本书教会了我用python!,而且print函数可以向文件输出！",file=pw_file)

result!

1,2,hello world!
这本书教会了我用python!,而且print函数可以向文件输出！

a python file object can be seen as an iterative - dealing with large text for loop

with open('E:\python_linux\s006_string_reguler_express.py',encoding = 'utf-8') as f:
    for line in f:
        print(line)