Python 学习入门（18）—— 字符串

Python判断字符串只包含数字

一种方法是 a.isdigit()，但这种方法对于包含正负号的数字字符串无效，更为准确的为：

#!/usr/bin/python# -*- coding:utf-8 -*-## http://blog.ithomer.netimport sysimport math# 判断是否为数字def isNum(value):    try:        value + 1    except TypeError:        return False    else:        return True# 判断是否为数字def isNum2(value):    try:        x = int(value)    except TypeError:        return False    except ValueError:        return False    except Exception, e:        return False    else:        return Truedef test1():        a = "123abcDE"    print a.isalnum()       # True, 所有字符都是数字或者字母    a = "abcDE"    print a.isalpha()       # True, 所有字符都是字母    a = "123.3"    print a.isdigit()       # False, 所有字符都是数字    a = "abcde"    print a.islower()       # True, 所有字符都是小写    a = "ABCDE"    print a.isupper()       # True, 所有字符都是大写    a = "Abcde"    print a.istitle()       # True, 所有单词都是首字母大写，像标题    a = "\t"    print a.isspace()       # True, 所有字符都是空白字符、\t、\n、\r    arr = (1, 2.1, -3, -4.5, '123a', 'abc', 'aBC', 'Abc', 'ABC', '\t')    for a in arr:        print a,isNum(a)    '''    1 True    2.1 True    -3 True    -4.5 True    123a False    abc False    aBC False    Abc False    ABC False        False    '''    for a in arr:        print a,isNum2(a)    '''    1 True    2.1 True    -3 True    -4.5 True    123a False    abc False    aBC False    Abc False    ABC False        False    '''

这样更准确一些，适用性也更广。但如果你已经确信没有正负号，使用字符串的isdigit()方法则更为方便。

Python 字符串操作，如string替换、删除、截取、复制、连接、比较、查找、包含、大小写转换、分割等

def test2():    # 复制字符串     str1 = "ithomer.net"    str2 = str1    str1 = "blog"    print str1, str2        # blog ithomer.net    # 连接字符串    str1 = "ithomer.net"    str2 = "blog."    str2 += str1    print str1, str2        # ithomer.net blog.ithomer.net        # 查找字符    str1 = "ithomer.net"    str2 = ".net"    pos = str1.index(str2)    print pos               # 7    # 比较字符串    str1 = "blog.ithomer.net"    str2 = "forum.ithomer.net"    pos = cmp(str1, str2)    print pos               # -1    # 是否包含指定的字符    str1 = "blog.ithomer.net"    str2 = ".ithomer."    pos = len(str1 and str2)    print pos               # 9    # 字符串长度    str1 = "blog.ithomer.net"    pos = len(str1)    print pos               # 16    # 字符串大小写转换    str1 = "blog.ithomer.net"    str2 = "BLOG.ithomer.NET"    print str1.upper()      # BLOG.ITHOMER.NET    print str2.lower()      # blog.ithomer.net    # 追加指定长度的字符串    str1 = "blog.ithomer.net"    str2 = "1234567"    n = 3    str1 += str2[0:n]    print str1,str2         # blog.ithomer.net123 1234567    # 字符串指定长度比较    str1 = "blog.ithomer.net"    str2 = "blog.ithomer.NET"    n = 11    print cmp(str1[0:n], str2[0:n])     # 0    # 复制指定长度的字符    str1 = "blog.ithomer.net"    str2 = ""    n = 12    print str1[0:n]         # blog.ithomer    # 将字符串前n个字符替换为指定的字符    str1 = "blog.ithomer.net"    ch = 'r'    n = 3    print n*ch + str1       # rrrblog.ithomer.net    # 扫描字符串     sStr = 'cekjgdklab'       sStr1 = 'gka'       nPos = -1     for c in sStr1:         print c    print nPos       # 翻转字符串     str1 = "ithomer.net"    str2 = str1[::-1]    print str1,str2         # ithomer.net ten.remohti    # 查找字符串    str1 = "ithomer.net"    str2 = ".net"    pos = str1.find(str2)    print pos               # 7        # 分割字符串    str1 = "blog.ithomer.net"    str2 = "."    str3 = str1[str1.find(str2) + 1:]    print str3              # ithomer.net    print str1.split(str2)  # ['blog', 'ithomer', 'net']    # 连接字符串    str1 = ['blog', 'ithomer', 'net']    str2 = "."    str3 = str2.join(str1)    print str3              # blog.ithomer.net    # 只显示字母与数字    str1 = "521.ithomer.NET $ @ # ! 1314"    fmt = "abcdefghijklmnopqrstuvwxyz0123456789"    for c in str1:        if not c in fmt:            str1 = str1.replace(c,'')    print str1              # 521ithomer1314

Python unicode字节串转成中文问题

Example 1:
>>> s = r"\u65b0\u6d6a\u5fae\u535a\u6ce8\u518c"
>>> s
'\\u65b0\\u6d6a\\u5fae\\u535a\\u6ce8\\u518c'
>>> print s
\u65b0\u6d6a\u5fae\u535a\u6ce8\u518c
>>> s = s.decode("unicode_escape");     #就是这个函数
>>> print s
新浪微博注册

Example 2:

>>> str_ = "Russopho\xe9bic, clichd and just pl\xe9ain stupid."

>>> print str_

Russopho?bic, clichd and just pl?ain stupid.

>>> str_ = str_.decode("unicode_escape")

>>> print str_

Russophoébic, clichd and just pléain stupid.

参考推荐：

Python字符串操作

Python difflib

python unicode字节串转成中文问题