Python基础（数字,字符串方法）

数字:

#二进制转十进制
a='100'
v=int(a,base=2)
print(v)

#当前数字的二进制至少有多少位
b=2
v2=b.bit_length()
print(v2)

字符串:

#首字母大写
a="kelvin"
v=a.capitalize()
print(v)

#终极无敌'大写'变'小写'---->casefold
b="KELVIN"
v1=b.casefold()
v2=b.lower()
print(v1)
print(v2)

#居中显示字符串
c="kelvin"
v3=c.center(50,"-") #第二个参数不填，默认空格
print(v3)

#查询在字符串中指定序列出现次数
d="kelvinvinkddq"
num=d.count("d")
print(num)

#判断是否以指定字符序列开头或者结尾
e="nihaoyahahakelvin"
v4=e.endswith("in")
v6=e.endswith("o")
v5=e.startswith("ni")
v7=e.startswith("ll")
print(v4)
print(v6)
print(v5)
print(v7)

#查找字符串中是否有指定序列
f="fsdhjheujfdkelvinvfs d"
num1=f.find("kelvin")
num2=f.find("fsdf")
print(num1)
print(num2)

#字符串格式化
g="i am {name},age {age}"
v8=g.format(name="alex",age=19)
v9=g.format_map({"name":"kelvin","age":21})
print(v8)
print(v9)

#返回指定序列索引，不存在则报错
a="kelvinalapplebanag"
v=a.index("w")
print(v)

str = "this2009";  # 字符中没有空格
print (str.isalnum());

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

str = "this";  # No space & digit in this string
print str.isalpha();

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

str = "123456";  # Only digit in this string
print str.isdigit();

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

str = "       "; 
print str.isspace();

str = "This is string example....wow!!!";
print str.isspace();

tr = "This Is String Example...Wow!!!";
print str.istitle();

str = "This is string example....wow!!!";
print str.istitle();

str = "-";
seq = ("a", "b", "c"); # 字符串序列
print str.join( seq );

str = "this is string example....wow!!!";

print str.ljust(50, '0');

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

from string import maketrans   # 必须调用 maketrans 函数。

intab = "aeiou"
outtab = "12345"
trantab = maketrans(intab, outtab)

str = "this is string example....wow!!!";
print str.translate(trantab);

以上实例输出结果如下：

th3s 3s str3ng 2x1mpl2....w4w!!!

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);

 
str = "00000003210Runoob01230000000"; 
print str.strip( '0' );  # 去除首尾字符 0
 
 
str2 = "   Runoob      ";   # 去除首尾空格
print str2.strip();

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

以上是经常使用的内置方法。