Python中字符串常用的方法

zhufeng518

　　capitalize() 方法返回一个字符串的copy，并且这个字符串的首字母大写。例如：

str = "this is string example....wow!!!";
print "str.capitalize() : ", str.capitalize()
#output result
str.capitalize() :  This is string example....wow!!!
　　
count() 方法返回子串在指定范围内出现的次数。例如：

str.count(sub, start=0,end=len(string))
　　 

str = "this is string example....wow!!!";
sub = "i";
print "str.count(sub, 4, 40) : ", str.count(sub, 4, 40)
sub = "wow";
print "str.count(sub) : ", str.count(sub)

#output result
str.count(sub, 4, 40) :  2
str.count(sub, 4, 40) :  1
　　 endswith() 判断在指定范围内，是否以子串结束。例如：
　　startswith()

str = "this is string example....wow!!!";
suffix = "wow!!!";
print str.endswith(suffix);
print str.endswith(suffix,20);
suffix = "is";
print str.endswith(suffix, 2, 4);
print str.endswith(suffix, 2, 6);
#output result
True
True
True
False
　　  find() 返回子串在指定范围内首次出现的位置，未查到返回-1。例如：

str.find(str, beg=0,end=len(string))
str1 = "this is string example....wow!!!";
str2 = "exam";
print str1.find(str2);
print str1.find(str2, 10);
print str1.find(str2, 40);
#result
15
15
-1
　　 index()返回子串在指定范围内首次出现的位置，未查到抛出异常。例如：

str.index(str, beg=0end=len(string))

str = "this is string example....wow!!!";
str = "exam";
print str.index(str);
print str.index(str, 10);
print str.index(str, 40);
#result
15
15
Traceback (most recent call last):
File "test.py", line 8, in
print str.index(str, 40);
ValueError: substring not found
isalnum()判断字符串是否全是字母和数字（要么全是字母，要么全是数字，要么全是数字和字母）例如：
str.isa1num()

str = "this2009";  # No space in this string
print str.isalnum();
str = "this is string example....wow!!!";
print str.isalnum();
#result
True
False
isalpha()方法判断字符串内容全是字母。例如：
str.isalpha()

str = "this";  # No space & digit in this string
print str.isalpha();
str = "this is string example....wow!!!";
print str.isalpha();
#result
True
False
isdecimal()和isnumeric()判断字符串是否全是数字，该字符串必须是unicode object。例如：
str.isdecimal()

str = u"this2009";  
print str.isdecimal();
str = u"23443434";
print str.isdecimal();
#result
False
True
 isdigit()判断字符串全部为数字。例如：
str.isdigit()

str = "123456";  # Only digit in this string
print str.isdigit();
str = "this is string example....wow!!!";
print str.isdigit();
#result
True
False
islower()判断字符串中所有的字母是否都是小写。 isupper() 判断字符串中所有的字母是否都是大写。例如:
str.islower()

str = "THIS is string example....wow!!!";
print str.islower();
str = "this is string example....wow!!!";
print str.islower();

#result
False
True
　　 isspace()判断字符串是否全是空白符，例如：

str.isspace()

str = "     \t\n"; #include tab,space
print str.isspace();
str = "This is string example....wow!!!";
print str.isspace();
#result
True
False
　　istitle()判断字符串中，每个单词的首字母是否都是大写。例如:

str.istitle()

str = "This Is String Example...Wow!!!";
print str.istitle();
str = "This is string example....wow!!!";
print str.istitle();
#result
True
False
　　 join()通过特殊字符把字符串连接起来，例如：

str.join(sequence)

str = "-";
seq = ("a", "b", "c"); # This is sequence of strings.
print str.join( seq );

#result
a-b-c
　　len(str) 计算字符串的长度。
　　str.lower()把所有的大写字母转成小写。
　　str.upper()把所有的小写字母转成大写。
　　swapcase() 方法是把字符串中的小写转成大写，大写转成小写。例如

str.swapcase();
str = "this is string example....wow!!!";
print str.swapcase();
str = "THIS IS STRING EXAMPLE....WOW!!!";
print str.swapcase();

#result
THIS IS STRING EXAMPLE....WOW!!!
this is string example....wow!!!
　　 
　　lstrip()去除掉字符串左边规定的字符，默认是空格。例如：
　　 rstrip()去除掉字符串右边规定的字符，默认是空格。
　　strip()去除掉两边规定的字符，默认是空格

str.rstrip([chars])
str.lstrip([chars])
str.strip([chars]);

str = "     this is string example....wow!!!     ";
print str.lstrip();
str = "88888888this is string example....wow!!!8888888";
print str.lstrip('8');

#result
this is string example....wow!!!
this is string example....wow!!!8888888

str = "     this is string example....wow!!!     ";
print str.rstrip();
str = "88888888this is string example....wow!!!8888888";
print str.rstrip('8');

#result
this is string example....wow!!!
88888888this is string example....wow!!!
　　 
　　 maketrans()看例子吧：例子中实际上是把对应的字母替换成数字。

str.maketrans(intab, outtab]);

from string import maketrans   # Required to call maketrans function.
intab = "aeiou"
outtab = "12345"
trantab = maketrans(intab, outtab)
str = "this is string example....wow!!!";
print str.translate(trantab);

#result
th3s 3s str3ng 2x1mpl2....w4w!!!
　　 
　　 max()返回字符串中最大的字母。例如：

max(str)

str = "this is really a string example....wow!!!";
print "Max character: " + max(str);
str = "this is a string example....wow!!!";
print "Max character: " + max(str);

#result
Max character: y
Max character: x
　　replace()用新字符替换旧字符

str.replace(old,new[, max]) max表示替换的个数

str = "this is string example....wow!!! this is really string";
print str.replace("is", "was");         
print str.replace("is", "was", 3);

#result
thwas was string example....wow!!! thwas was really string
thwas was string example....wow!!! thwas is really string
　　rfind()返回指定指定范围内，子串最后出现的索引，找不到返回-1。例如：

str.rfind(str, beg=0end=len(string))

str = "this is really a string example....wow!!!";
str1 = "is";
print str.rfind(str1);
print str.rfind(str1, 0, 10);
print str.rfind(str1, 10, 0);
print str.find(str1);
print str.find(str1, 0, 10);
print str.find(str1, 10, 0);
#result
5
5
-1
2
2
-1
　　 rjust()看例子吧：

str.rjust(width[, fillchar])

str = "this is string example....wow!!!";
print str.rjust(50, '0');

#result
000000000000000000this is string example....wow!!!
　　zfill()用“0”进行填充。看例子吧：

str.zfill(width)

str = "this is string example....wow!!!";
print str.zfill(40);
print str.zfill(50);
#result
00000000this is string example....wow!!!
000000000000000000this is string example....wow!!!
　　
　　 
　　 split()按指定的分隔符分隔字符串，最终返回一个列表。例如：

str.split(str="", num=string.count(str)).num代表分隔的次数

str = "Line1-abcdef \nLine2-abc \nLine4-abcd";
print str.split( );
print str.split(' ', 1 );

#result
['Line1-abcdef', 'Line2-abc', 'Line4-abcd']
['Line1-abcdef', '\nLine2-abc \nLine4-abcd']
　　 title() 把字符串中每个单词的首字母大写。例如：

str.title();

str = "this is string example....wow!!!";
print str.title();
#result
This Is String Example....Wow!
　　 translate()看例子吧

str.translate(table[, deletechars]);

from string import maketrans   # Required to call maketrans function.
intab = "aeiou"
outtab = "12345"
trantab = maketrans(intab, outtab)
str = "this is string example....wow!!!";
print str.translate(trantab, 'xm');
#result
th3s 3s str3ng 21pl2....w4w!!!