Exercise 15 python
代碼函數
from sys import argv script, filename = argv txt = open(filename) print "Here is your file %r:" % filename print txt.read() print "Type the filename again:" file_again = raw_input("> ") txt_again = open(file_again) print txt_again.read()
輸出code
Notes:對象
①查看python文檔,python提示打開文件的首選方法是open(name[,mode[,buffering]])函數
three
②文件對象.read()方法讀取文件內容,有一個可選參數選擇讀取的長度,語法爲file.read([size])ip
③在python的交互模式中打開文件,需輸入文件的完整目錄
ci
>>> txt = open("E:\\code\\LPTHW\\ex15_sample.txt") >>> print txt.read() One Two Three
④文件對象.close()用於保存並關閉文件,在對文件操做完成後關閉文件文檔
Exercise 16字符串
代碼
get
from sys import argv script, filename = argv print "We're going to erase %r." % filename print "If you don't want that, hit CTRL-C (^C)." print "If you do want that, hit RETURN." raw_input("?") print "Opening the file..." target = open(filename,"w") print "Truncating the file. Goodbye!" target.truncate() print "Now I'm going to ask you for three lines." line1 = raw_input("Line 1: ") line2 = raw_input("Line 2: ") line3 = raw_input("Line 3: ") print "I'm going to write these to the file." target.write(line1) target.write('\n') target.write(line2) target.write("\n") target.write(line3) target.write("\n") print "And finally, we close it." target.close()
輸出
Notes:
①文件對象.truncate()方法會清除文件內容
②write()方法把括號中的字符串對象寫入文件中,字符串對象支持格式化及轉義操做
③open()打開模式'w'表示也寫的方式打開,文件不存在會被建立,已存在會在打開時清空內容。不添加打開參數時,open()默認以只讀的方式打開文件
Exercise 17
代碼
from sys import argv from os.path import exists script, from_file, to_file = argv print "Copying from %s to %s" % (from_file,to_file) # we could do these two on one line, how? in_file = open(from_file) indata = in_file.read() print "The input file is %d bytes long" % len(indata) print "Does the output file exist? %r" % exists(to_file) print "Ready, hit RETURN to continue, CTRL-C to abort." raw_input() out_file = open(to_file,"w") out_file.write(indata) print "Alright, all done." out_file.close() in_file.close()
輸出
Notes:
①os.path模塊中的exists()函數用來判斷一個文件是否存在,存在返回True,不然返回False