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：
<span style="color: rgb(51, 51, 51); font-family: Verdana, 'Lucida Grande', Lucida, Helvetica, Arial, sans-serif; font-size: 13px; line-height: 19.5px;">#!/usr/bin/python
# -*- coding:utf-8 -*-
#
# http://blog.ithomer.net
import sys
import math
# 判断是否为数字
def isNum(value):
try:
value + 1
except TypeError:
returnFalse
else:
returnTrue
# 判断是否为数字
def isNum2(value):
try:
x = int(value)
except TypeError:
returnFalse
except ValueError:
returnFalse
except Exception, e:
returnFalse
else:
returnTrue
def 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
'''</span>
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:
ifnot c in fmt:
str1 = str1.replace(c,'')
print str1 # 521ithomer131