python拼接字符串

https://www.cnblogs.com/jamsent/p/7183905.html

fruit1 = 'apples'
fruit2 = 'bananas'
fruit3 = 'pears'

1. 用+符号拼接
   用+拼接字符串如下：

str = 'There are'+fruit1+','+fruit2+','+fruit3+' on the table'
该方法效率比较低，不建议使用

2. 用%符号拼接
   str = 'There are %s, %s, %s on the table.' % (fruit1,fruit2,fruit3)
   除了用元组的方法，还可以使用字典如下：

str = 'There are %(fruit1)s,%(fruit2)s,%(fruit3)s on the table' % {'fruit1':fruit1,'fruit2':fruit2,'fruit3':fruit3}

3. 用join()方法拼接
   join()`方法拼接如下

temp = ['There are ',fruit1,',',fruit2,',',fruit3,' on the table']
''.join(temp)
该方法使用与序列操作

4. 用format()方法拼接
   用format()方法拼接如下:

1 str = 'There are {}, {}, {} on the table'
2 str.format(fruit1,fruit2,fruit3)

还可以指定参数对应位置：
str = 'There are {2}, {1}, {0} on the table'
str.format(fruit1,fruit2,fruit3) #fruit1出现在0的位置

同样，也可以使用字典：
str = 'There are {fruit1}, {fruit2}, {fruit3} on the table'
str.format(fruit1=fruit1,fruit2=fruit2,fruit3=fruit3)