python中字符串的合并（f字符串，在变量中使用字符串）

>>> a = "string1"
>>> b = "string2"
>>> print(ab)  ## 直接输出报错
Traceback (most recent call last):
  File "<pyshell#33>", line 1, in <module>
    print(ab)
NameError: name 'ab' is not defined
>>> ab = f"{a} {b}"   ## 使用f合并字符串
>>> print(ab)
string1 string2
>>> print(ab,"strints")
string1 string2 strints
>>> print(f"{ab} strints")
string1 string2 strints

>>> print("xxxx")
xxxx
>>> print("yyyy")
yyyy
>>> print("xxxx""yyyy")
xxxxyyyy
>>> print("xxxx","yyyy")
xxxx yyyy
>>> a = "mmmm"
>>> b = "nnnn"
>>> c = "oooo"
>>> print(bc)
Traceback (most recent call last):
  File "<pyshell#111>", line 1, in <module>
    print(bc)
NameError: name 'bc' is not defined
>>> print(b,c)
nnnn oooo
>>> print(a,b,c)
mmmm nnnn oooo