Q1:

(ex8)
不赋值的串也可以输出？
针对如下代码：


formatter="%r %r %r %r"  
print formatter %(formatter,formatter,formatter,formatter)
</code>

Q2:

(ex15) 


from sys import argv

script, filename = argv txt = open(filename)

print "Here's 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() </pre></code>

为什么注释掉import也可以运行？

Q3:

(ex16) 


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() </pre></code>

为什么将truncate注释之后还是会清空文件呢？

Answer：

【15.10.21】 'w'会清空，'a'则不会。

Q4:

(ex17) 


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 too, how? input = open(from_file) indata = input.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()

output = open(to_file, 'w') output.write(indata)

print "Alright, all done."

output.close() input.close() </pre></code>

为什么只能用print indata而不能用output.read()或open(to_file).read()？给出的提示信息是：File not open for reading.

Q5:

(ex20) 


from sys import argv

script, input_file = argv

def print_all(f): print f.read()

def rewind(f): f.seek(0)

def print_a_line(line_count, f): print line_count, f.readline()

current_file = open(input_file)

print "First let's print the whole file:\n"

print_all(current_file)

print "Now let's rewind, kind of like a tape."

rewind(current_file)

print "Let's print three lines:"

current_line = 1 print_a_line(current_line, current_file)

current_line = current_line + 1 print_a_line(current_line, current_file)

current_line = current_line + 1 print_a_line(current_line, current_file) </pre></code>

怎么才能让readline()所读取的内容与行号参数有关？

Q6:

(ex20)
起始行号为什么不是0而是1？

Q7:

raw_input中出现“小”和“大”字无法打印出来，但直接print“小”和“大”可以。why？