python中常用的字符串和使用方法

字符串

字符串方法format，替代字符串用花括号括起来，
"{}, {}, and {}".format("first", “second”, "third")，替换字段没有索引或者名称则按顺序替换，若有索引或名称，就按索引和名称替换。

# 无索引按默认顺序替换
txt = "{},{}, and {}"
txt.format("first","second","third")
>>> 'first,second, and third'

# 索引替换
txt = "{1},{2},{0}, and {1}"
txt.format("first","second","third")
>>> 'second,third,first, and second'

# 按名称替换
txt = "{name} is approximately {value: .2f}"
txt.format(value = pi, name = "π")
>>> 'π is approximately  3.14'

字符串方法
txt.center(width, "symbol")：居中，width：表示宽度；
txt.ljust(width, "symbol")：居左；
txt.rjust(width, "symbol")：居右；
txt.zfill(width)：居右，空位用0填充；
txt.find("xxx", start, end)：在字符串中找子串，返回第一个字符的索引，如果没有就返回-1；
join：合并序列

seq = ["1", "2", "3", "4"]
sep = '+'
sep.join(seq)
>>> '1+2+3+4'

7. txt.lower()：返回小写字母；
8. txt.title()：词首字母大写；
9. txt.replace('old', 'new')：替换；
10. split：拆除

'1+2+3+4'.split('+')
>>> ["1", "2", "3", "4"]

11. txt.strip()：删除开头和结尾的空白；
12. translate：

from string import maketrans   # 引用 maketrans 函数。
 
intab = "aeiou"
outtab = "12345"
trantab = maketrans(intab, outtab)
 
str = "this is string example....wow!!!";
print str.translate(trantab);

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

[resource:](https://www.runoob.com/python/att-string-translate.html)

判断是否符合条件，返回布尔值的方法。
isdigit、islower、istitle等等…

原文链接：https://blog.csdn.net/leeyns/article/details/106169733