• 学习测试开发的Day98，真棒！
• 学习时间为50M
• 第九次全天课(下午视频二50M-1H34M）

打开文件 with写法

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>>> with open("e:\\a.txt","r") as fp:
...     fp.read()
...
'13872609001\n13775543001\n13664816001\n13857078001\n13510637001\n13781757001\n13549218001\n13889925001\n13502528001\n13882106001\n13848872001\n13549574001\n13823995001\n13582873001\n13819646001\n13710061001\n13509171001\n13602171001\n13758653001\n13573609001\n13880029001\n13843230001\n13842306001\n13598729001\n13836264001\n13651560001\n13843554001\n13889717001\n13502836001\n13787472001\n13606495001\n13869416001\n13820985001\n13703184001\n13804662001\n13857096001\n13776800001\n13828410001\n13740832001\n13865852001\n13849526001\n13503163001\n13734256001\n13815249001\n13884905001\n13570427001\n13711766001\n13662375001\n13867401001\n13894115001\n13783949001\n13756633001\n13892140001\n13558068001\n13588846001\n13669064001\n13546868001\n13543669001\n13756314001\n13670332001\n13775690001\n13664445001\n13550739001\n13576244001\n13742917001\n13820262001\n13722884001\n13503369001\n13687175001\n13582656001\n13746025001\n13649502001\n13879751001\n13875025001\n13630594001\n13739944001\n13822684001\n13604358001\n13562272001\n13888727001\n13898369001\n13671814001\n13764822001\n13650445001\n13581385001\n13703916001\n13685986001\n13822300001\n13747323001\n13883401001\n13795773001\n13502369001\n13766082001\n13756944001\n13829542001\n13848739001\n13544240001\n13588486001\n13607725001\n13643311001\n'
>>>

with写完不用关文件，with自动关

with的原理

class Sample:
    def __enter__(self):
        print("In__enter__()")
        return "Foo"

    def __exit__(self,type,value,trace):
        print("In __exit__()")

def get_sample():
        return Sample()
with get_sample() as sample:
    print("sample:",sample)

输出：

PS D:\0grory\day9> python .\sample.py
In__enter__()
sample: Foo
In __exit__()
PS D:\0grory\day9>

write 之所以不用关，是因为在————exit__中给关了

文件操作模式

image.png

文件对象

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>>> fp=open("e:\\a.txt")
>>> fp.closed
False
>>>
>>> fp.mode
'r'
>>> fp.name
'e:\\a.txt'
>>>

>>> dir(fp)
['_CHUNK_SIZE', '__class__', '__del__', '__delattr__', '__dict__', '__dir__', '__doc__', '__enter__', '__eq__', '__exit__', '__format__', '__ge__', '__getattribute__', '__getstate__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__lt__', '__ne__', '__new__', '__next__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_checkClosed', '_checkReadable', '_checkSeekable', '_checkWritable', '_finalizing', 'buffer', 'close', 'closed', 'detach', 'encoding', 'errors', 'fileno', 'flush', 'isatty', 'line_buffering', 'mode', 'name', 'newlines', 'read', 'readable', 'readline', 'readlines', 'seek', 'seekable', 'tell', 'truncate', 'writable', 'write', 'writelines']
>>>

文件操作的常用方法-read

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>>> fp
<_io.TextIOWrapper name='e:\\a.txt' mode='r' encoding='cp936'>
>>> fp.read(5)
'13872'
>>> fp.read()
'609001\n13775543001\n13664816001\n13857078001\n13510637001\n13781757001\n13549218001\n13889925001\n13502528001\n13882106001\n13848872001\n13549574001\n13823995001\n13582873001\n13819646001\n13710061001\n13509171001\n13602171001\n13758653001\n13573609001\n'
>>> fp.read()
''
>>> fp.seek(0,0)
0
>>> fp.read(5)
'13872'
>>> fp.read(5)
'60900'
>>> fp.read(5)
'1\n137'

readlines

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>>> fp.readlines()
['75543001\n', '13664816001\n', '13857078001\n', '13510637001\n', '13781757001\n', '13549218001\n', '13889925001\n', '13502528001\n', '13882106001\n', '13848872001\n', '13549574001\n', '13823995001\n', '13582873001\n', '13819646001\n', '13710061001\n', '13509171001\n', '13602171001\n', '13758653001\n', '13573609001\n', '13880029001\n', '13843230001\n', '13842306001\n', '13598729001\n', '13836264001\n', '13651560001\n', ]

>>> fp.seek(0,0)
0
>>> fp.readlines()[2]
'13664816001\n'
>>>
>>> fp.seek(0,0)
0
>>> len(fp.readlines())#算行数
100
>>>

读出全部内容和逐行显示

#encoding=utf-8

fp=open("e:\\a.txt",'r')
contentList=fp.readlines()

print("读取文件的内容:\n",contentList)
for i in contentList:
    print(i)

##关闭文件
fp.close()

输出：

PS D:\0grory\day9> python .\readlines.py
读取文件的内容:
 ['13872609001\n', '13775543001\n', '13664816001\n', '13857078001\n', '13510637001\n', '13781757001\n', '13549218001\n', '13889925001\n', '13502528001\n', '13882106001\n', '13848872001\n', '13549574001\n', '13823995001\n', '13582873001\n', '13819646001\n', '13710061001\n', '13509171001\n', '13602171001\n', '13758653001\n', '13573609001\n', '13880029001\n']
13872609001

13775543001

13664816001

readline

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一般行读很少指定行数

>>> fp.seek(0,0)
0
>>> fp.readline(5)
'13872'
>>> fp.readline(5)
'60900'
>>> fp.readline(5)
'1\n'
>>>

write

fileObject.write( str )

把str写到文件中，默认是不加换行符的，所以如果想换行的话，得手动加入
换行符'\n'。

代码示例：

#encoding=utf-8
fp = open( "d:\\0grory\\day9\\test.txt",'w') 
fp.write('文件写入测试' + '\n')
#关闭文件
fp.close()

image.png

writelines

fileObject.writelines( seq )

把seq（序列）的内容全部写到文件中（多行一次性写入）。也不会自动
加入换行符。

代码示例：

#encoding=utf-8
testList = ['abcede\n', '123\n', 'this is a test', '文件操作']
#打开文件准备写文件
fp = open( "c:\\test.txt",'w') 
#将列表testList所有内容一次全部写入文件
fp.writelines( testList )
#关闭文件
fp.close()

更多解释：

注意：序列中的内容也必须是字符串类型的数据，才能成功写入文件。

>>> fp=open("d:\\0grory\\day9\\test2.txt","w")
>>> fp.write("hi")
2
>>> fp.writelines(["ab\n","cd\n","ef\n"])
>>> fp.close()
>>> fp=open("d:\\0grory\\day9\\test2.txt","r")
>>> fp.read()
'hiab\ncd\nef\n'
>>>