python---布尔类型赋值，字符串，len()，转义、拼接、替换、文件操作

python—布尔类型赋值，字符串，len()，转义、拼接、替换、文件操作

#1、布尔类型root@72132server:~# pythonPython 2.7.3 (default, Mar 14 2014, 11:57:14) [GCC 4.7.2] on linux2Type "help", "copyright", "credits" or "license" for more information.>>> bool(1==1)True>>> a = bool(2==2)#使用参数求值>>> aTrue>>> #2、字符串认知与应用python默认的文件编码都是ascii码unicode 描述出大部分全世界语音utf8是unicode的一种标准#3、len使用技巧--注意root@72132server:~# clearroot@72132server:~# pythonPython 2.7.3 (default, Mar 14 2014, 11:57:14) [GCC 4.7.2] on linux2Type "help", "copyright", "credits" or "license" for more information.>>> a = '1234'>>> len(a)4>>> b = '哈哈哈我是中国人'>>> len(b)24>>> c = '哈'>>> len(c)3>>> d = u'哈'>>> len(d)1>>> e = '哈哈哈哈'>>> f = e.decode('utf-8')>>> print f哈哈哈哈>>> print len(f)4>>> >>> >>> h = '哼哼哈哈'>>> h = '哼哼哈哈'.decode('utf-8')>>> print len(h)4>>> len(h)4>>> j = '哈哈哈哈'>>> len(j)12>>> #4、转义字符让文本更好处理#\要放到需要转义的字符前面>>> print 'adbcd'adbcd>>> print 'aasff''  File "<stdin>", line 1    print 'aasff''                 ^SyntaxError: EOL while scanning string literal>>> print 'aasff'\'  File "<stdin>", line 1    print 'aasff'\'                  ^SyntaxError: unexpected character after line continuation character>>> print 'aasff\''aasff'>>> print 'asdf\n'asdf>>> print 'asdf\t'asdf    >>> print 'asdf\f'asdf>>> print 'asdf\2t'asdft>>> print 'asdf\2n'asdfn>>> #\要放到需要转义的字符前面#5、字符串前面跟着的小尾巴到底是什么东西#u是把后面的字符串转成unicode码#r是把后面的字符串不进行转义，原样输出>>> >>> i = u'哈哈'>>> iu'\u54c8\u54c8'>>> print '\n'>>> print r'\n'\n>>> #6、访问子字符串，序列来了，使用切片方式访问成员是有序排列的，可以通过下标偏移量访问到它的一个或者多个成员>>> l = 'asdfgh'>>> l[2]'d'>>> l[0]'a'>>> l[-1]'h'>>> l[-2]'g'>>> l[2,4]Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: string indices must be integers, not tuple>>> l[2:4]'df'>>> print l[0]a>>> print l[-2:3]>>> print l[-2:-3]>>> print l[-1:3]>>> print l[-1]h>>> len(l)6>>> l[0:4]'asdf'>>> l[-1:4]''>>> l[-1:-3]''>>> l[0:-3]'asd'>>> l[0:-1]'asdfg'>>> l[0:]'asdfgh'>>> l[0:-4]'as'>>> l[:-1]'asdfg'>>> m = '123456789'>>> m[3]'4'>>> m[5]'6'>>> m[6] - m[2]Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: unsupported operand type(s) for -: 'str' and 'str'>>> n = m[6] - m[2]Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: unsupported operand type(s) for -: 'str' and 'str'>>> #使用N种方式取出字母d>>> y = 'abcd'>>> y[1]'b'>>> y[3]'d'>>> y[-1]'d'>>> y[-1:-2]''>>> y[-1:]'d'>>> y[3:]'d'>>> #使用split分割进行显示>>> s ='i am lilei!!'>>> s[2:4]'am'>>> b = s.split(' ')[1]>>> print bam>>> b = s.split(' ')[2]>>> print blilei!!>>> #7、替换字符串，使用help进行帮助查看>>> help('str')>>> help('str')>>>  |  replace(...) |      S.replace(old, new[, count]) -> string |       |      Return a copy of string S with all occurrences of substring |      old replaced by new.  If the optional argument count is |      given, only the first count occurrences are replaced.>>> o = 'abcdefg'>>> o.replace('c','xwbxwb')'abxwbxwbdefg'>>> print o #没有变化的字符串abcdefg>>> p = o.replace('c','xwbxwb')>>> id(a)3074941920L>>> id(o)3074987488L>>> id(p)3074934688L>>> >>> print p #新的字符串abxwbxwbdefg>>> #8、字符串拼接#8.1、超级丑陋方式，千万别用>>> >>> q = 'abcd'>>> r = 'uvwxyz'>>> print q+rabcduvwxyz>>> print 'rst'+'kiopq'rstkiopq>>> #8.2、可选方案之字符串模版，使用%s占位符>>> print 'my name is %s lilei.' %'hanmeimei'my name is hanmeimei lilei.>>> >>> print 'my name is %d lilei.' %1my name is 1 lilei.>>> print 'my name is %d lilei.' %'ss'Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: %d format: a number is required, not str>>> print 'my name is %d lilei.' %55555my name is 55555 lilei.>>> >>>> print 'my name is %s lilei %s.' % ('hanmeimei','20')my name is hanmeimei lilei 20.>>> >>> z = 'jay'>>> a = 'python'>>> print 'my name is %s ,i love %s.' % ('z','a')my name is z ,i love a.>>> print 'my name is %s ,i love %s.' % (z,a)my name is jay ,i love python.>>> %s表示是占位符#8.3、优秀的拼接方案，推荐使用最完美的方式>>> u = 'a'>>> v = 'bcdef' >>> w = '123456'>>> "".join(u,v,w)Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: join() takes exactly one argument (3 given)>>> ",".join([u,v,w])#使用List方式进行拼接'a,bcdef,123456'>>> "".join([u,v,w])'abcdef123456'>>> #9、读写文件操作r read(读)w write(写)a append(在尾行添加)>>> open('/root/python/oldtext.txt','w')<open file '/root/python/oldtext.txt', mode 'w' at 0xb746e860>>>> x =open('/root/python/oldtext.txt','w')>>> x.write('my name is da xue sheng!!')>>> x.close()>>> x = open('/root/python/oldtext.txt','r')>>> help (x)>>> print x.readline()my name is da xue sheng!!>>> print x.readline()>>> print x.readline()>>> print x.read(1000)>>> x.seek(0)#把读取游标设置到初始位置>>> print x.read(1000)my name is da xue sheng!!>>> 综合练习题：

a.find()、a.index()、a.rfind()查找语句使用a.find()与a.index()区别：a.find()未找到的字符直接返回-1a.index()未找到的字符报错root@kali:~/python/laowangpy# pythonPython 2.7.3 (default, Mar 14 2014, 11:57:14) [GCC 4.7.2] on linux2Type "help", "copyright", "credits" or "license" for more information.>>> import string>>> help(string)>>> a = 'i am boy from china'>>> a.find('i')0>>> a.find('i')0>>> a.index('i')0>>> a.find('i',a.find('china'))16>>> a.rfind('i')16>>> a.count(' ')4>>> a.find('m')3>>> a.find('j')-1>>> a.index('m')3>>> a.index('j')Traceback (most recent call last):  File "<stdin>", line 1, in <module>ValueError: substring not found>>> 

root@kali:~/python/laowangpy# ls
geshihua.py hello.py _project test1.txt test2.txt test_uncode.py
root@kali:~/python/laowangpy# cat test_uncode.py
3#!/usr/bin/python
3#—- coding:utf-8 —-

f = open(“/root/python/laowangpy/test1.txt”,’r’)
content = f.read()
dcontent = content.decode(“utf-8”)#转载成unicode编码

print “–#1、输出内容–”
print content

print “–#2、计算该文件的原始长度–”
print len(content)

print “–#3、请除去该文本的换行符号–”
print content.replace(‘\n’,”)

print “–#4、请替换其中的字符‘2012’为‘2013’–”
print content.replace(‘2012’,’2013’)

print “–#5、请取出最中间的长度为5的字串–”
print dcontent[len(dcontent)/2:len(dcontent)/2+5].encode(“utf-8”)

print “–#6、请取出最后两个字符–”
print dcontent[-2:].encode(“utf-8”)

print “–#7、请从字符串的最初开始，截断该字符串，使其长度为11–”
print dcontent[0:10].encode(“utf-8”)

print “–8、请将#4题中的字符串保存为test2.py文本–”
rinfo = content.replace(‘2012’,’2013’)
print rinfo
f1 = open(‘/root/python/laowangpy/test2.txt’,’w’)
f1.write(rinfo)
f1.close()

root@kali:~/python/laowangpy#

运行情况：
root@kali:~/python/laowangpy# python test_uncode.py
–#1、输出内容–
2012来了。
2012不是世界末日。
2012欢乐多。

–#2、计算该文件的原始长度–
57
–#3、请除去该文本的换行符号–
2012来了。2012不是世界末日。2012欢乐多。
–#4、请替换其中的字符‘2012’为‘2013’–
2013来了。
2013不是世界末日。
2013欢乐多。

–#5、请取出最中间的长度为5的字串–
世界末日。
–#6、请取出最后两个字符–
。

–#7、请从字符串的最初开始，截断该字符串，使其长度为11–
2012来了。
20
–8、请将#4题中的字符串保存为test2.py文本–
2013来了。
2013不是世界末日。
2013欢乐多。

root@kali:~/python/laowangpy# cat test2.txt
2013来了。
2013不是世界末日。
2013欢乐多。