输出
repr和str
str()和repr()都是将参数转化为字符串
如果参数本身为字符串,两种用法会有区别
>>> t = 'hallo,world'>>> t'hallo,world'>>> str(t)'hallo,world'>>> repr(t)"'hallo,world'"
如果参数为浮点数,保留的位数会有区别
>>> str(1.0/7.0)'0.142857142857'>>> repr(1.0/7.0)'0.14285714285714285'
对于其他情况,两种用法得到结果相同
>>> str(23)'23'>>> repr(23)'23'
字符串格式函数
rjust(width)
右对齐,width为字符快递,超过宽度则能对齐多少多起多少>>> for x in range(5,12):... print str(x).rjust(2)... 5 6 7 8 91011>>> for x in range(5,12):... print str(x).rjust(1)... 5678910 #超过了宽度,能对齐一位就对齐一位,11>>> for x in range(1,200,30):... print str(x).rjust(2)... 1316191121151181
类似用法还有rjust(width)
format()#基本用法>>> print 'someone call me {} but others call me {}!'.format('song','lige')someone call me song but others call me lige!>>> print 'someone call me {0} but others call me {1}!'.format('song','lige')someone call me song but others call me lige!>>> print 'someone call me {1} but others call me {0}!'.format('song','lige')someone call me lige but others call me song!>>> print 'someone call me {realname} but others call me {virtname}!'.format(realname = 'song',virtname ='lige')someone call me song but others call me lige!>>> import math>>> print 'the value of PI is {}'.format(math.pi)the value of PI is 3.14159265359>>> print 'the value of PI is {:.4f}'.format(math.pi)the value of PI is 3.1416 # 与字典参数结合>>> for name, grade in grade.items():... print '{0:10} ---> {1:10d}'.format(name, grade)... wu ---> 92leng ---> 99song ---> 88 %
也可以用%来格式化字符串>>> print 'value of PI is %d' % math.pivalue of PI is 3>>> print 'value of PI is %.3f' % math.pivalue of PI is 3.142
文件读写
open函数
#用法和C语言类似>>> f = open('E:\\test_for_filefun.txt','rb+')>>> f.write('this is a test\n')>>> f.close()>>> f = open('E:\\test_for_filefun.txt','rb+')>>> f.read()'this is a test\n'>>> f.readline()'' #读不到东西的时候返回''空字符串 相关的函数
- f.tell() 返回文件指针到文件开头的比特数目
- f.seek(offset, from_what)
from_what参数0,表示自文件开头开始,1表示从当前文件指针的位置开始,2表示从文件末尾开始
>>> f = open('E:\\test_for_filefun.txt','rb+')>>> f.readline()"['192.168.1.1', '192.168.1.2', '192.168.1.176']\n">>> f.tell()48L>>> f.seek(40)>>> f.read(8)"1.176']\n" 小技巧
利用with参数处理文件
文件用完了之后会自动关闭>>> with open('E:\\test_for_filefun.txt','rb+') as f:... print f.readline()... ['192.168.1.1', '192.168.1.2', '192.168.1.176']>>> f.closed #f.closed可以用来判断文件是否关闭True #发现with语句执行完了之后文件的确关闭了 pickle模块
由于不同数据类型和字符串之间的转换很麻烦
所以引入了pickle模块:封装和解封pickle.dump(x,fp)是将文件对象f封装到x中,然后x就是一个字符串,可以用来传递写入等操作x = pickle.load(fp)从f中读取一个字符串,并且将它重构为python对象