python tutorial 学习笔记（四） Input and Output, 字符串的转换等

print object value in the interpreter shell:

• expression statment
• print keyword
• print a,b,c
• sys.stdout.write()

string module

transfer objects to string

str() function: human readble

repr() function: can be read by the interpreter

string formatting

str.format() “{0} and {1}”.format("spam", "eggs")

>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 7678}

>>> for name, phone in table.items():

... print '{0:10} ==> {1:10d}'.format(name, phone)

...

Jack ==> 4098

Dcab ==> 7678

Sjoerd ==> 4127

print 'This {food} is {adjective}.format( food='spam', adjective='absolutely horrible')

old style

print '%i != %i.' % (1,2)

Methods of File Objects

open( filename,mode) mode can be “r””w””a””r+”(both reading and wrting)”

On Windows, text file and binary files are treated differently. The end-of-line characters in text files are automatically altered slightly when read or written. This behind-the-scenes modification will currupt binary data like that in JPEG or EXE files. So this kind of file need to be opened with “b” mode (binary mode).

f.read([size]), read size of bytes, return “” at the end of the file

f.readline(), return “” at the end of file, return “/n” while blank line.

f.readlines([sizeint])

for line in f: print line

f.write(string),

f.seek(offset,from_what), f.tell()

f.close()