python學習筆記文件操作(六)
1、文件操作流程:
打開文件,得到文件句柄並賦值給一個變量
通過句柄對文件進行操作
關閉文件
如下文件:
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"} 2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap 2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator 2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state ‘stopping‘ 2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"} 2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
操作流程:
f = open(‘log.txt‘,‘r‘) print(f.read()) f.close()
註意: 在win系統中log文件是utf8保存的,打開文件時open函數是通過操作系統打開的文件,而win操作系統默認的是gbk編碼,所以直接打開會亂碼,需要f=open(‘hello‘,encoding=‘utf8‘),hello文件如果是gbk保存的,則直接打開即可。
2、文件打開模式
# ========= =============================================================== # # Character Meaning # # --------- --------------------------------------------------------------- # # ‘r‘ open for reading (default) # # ‘w‘ open for writing, truncating the file first # # ‘x‘ create a new file and open it for writing # # ‘a‘ open for writing, appending to the end of the file if it exists # # ‘b‘ binary mode # # ‘t‘ text mode (default) # # ‘+‘ open a disk file for updating (reading and writing) # # ‘U‘ universal newline mode (deprecated) # # ========= ===============================================================
3、文件操作方法
獲取文件內容
f = open(‘log.txt‘,‘r‘) data = f.read() print(data) f.close()
輸出:
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state ‘stopping‘
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
f = open(‘log.txt‘,‘r‘) data1 = f.read(10) #讀取10個字符。(在這裏漢字也只占一個單位) print(data1) f.close()
輸出:
2017-03-24
readline和readlines
===========================================================================================
f = open(‘log.txt‘,‘r‘) print(f.readlines()) #返回的是一個列表,註意換行符 f.close()
輸出:
[‘2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}\n‘, ‘2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap\n‘, ‘2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator\n‘, "2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state ‘stopping‘\n", ‘2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}\n‘, ‘2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN‘]
===========================================================================================
f = open(‘log.txt‘,‘r‘) print(f.readline()) #逐行讀取 print(f.readline()) print(f.readline(),f.readline(),f.readline()) #逐行讀取,每行末尾換行符 f.close()
輸出:(註意每行末尾的換行符)
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state ‘stopping‘
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
===========================================================================================
f = open(‘log.txt‘,‘r‘) for line in f.readlines(): print(line.strip()) f.close()
輸出:
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state ‘stopping‘
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
f = open(‘log.txt‘,‘r‘) print(f) for i in f: print(i.strip()) f.close()
輸出:
<_io.TextIOWrapper name=‘log.txt‘ mode=‘r‘ encoding=‘cp936‘>
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state ‘stopping‘
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
n = 0 f = open(‘log.txt‘,‘r‘) for i in f: if n == 3: i = ‘‘.join([i.strip(),‘ this is line 4‘]) print(i.strip()) n += 1 f.close()
輸出:
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state ‘stopping‘ this is line 4
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
tell和seek
f = open(‘log.txt‘,‘r‘) print(f.read(25)) print(f.tell()) #取出光標所在位置 print(f.seek(0)) #移動光標到指定的位置 print(f.read(50)) f.close()
輸出:
2017-03-24 11:25:06:349 -
25
0
2017-03-24 11:25:06:349 - info: [debug] [AndroidBo
註意:read後不管是中文字符還是英文字符,都統一算一個單位,read(6),此刻就讀了6個中文字符;而seek和tell對於英文字符就是占一個,中文字符占三個,區分與read()的不同.
===========================================================================================
flush:同步把數據從緩存移動到磁盤上去
#進度條實例 import sys,time for i in range(30): sys.stdout.write("*") sys.stdout.flush() time.sleep(0.1) #print的flush import sys,time for i in range(30): print(‘*‘,end=‘‘,flush=True) time.sleep(0.1)
===========================================================================================
其他擴展:
#truncate():截斷數據(不能在r模式下)
#在w模式下:先清空,再寫,再截斷
#在a模式下:直接將指定位置後的內容截斷
# r+:光標默認在0位置開始寫,從0開始覆蓋數據
# w+:先清空,再寫讀
# a+:光標默認在最後位置
===========================================================================================
with:
為了避免打開文件後忘記關閉,可以通過管理上下文,即:
with open(‘log.txt‘,‘r‘) as f: print(f.readline())
在Python 2.7 後,with又支持同時對多個文件的上下文進行管理,即:如此方式,當with代碼塊執行完畢時,內部會自動關閉並釋放文件資源。
#with 同時管理多個文件對象 with open(‘log1‘,‘r‘) as f_read, open(‘log2‘,‘w‘) as f_write: for line in f_read: f_write.write(line)
本文出自 “on_the_road” 博客,請務必保留此出處http://cqtesting.blog.51cto.com/8685091/1959698
python學習筆記文件操作(六)