how to use concatenate a fixed string and a variable in Python

问题

I want to include file name 'main.txt' in the subject for that I am passing file name from command line. but getting error in doing so

python sample.py main.txt #running python with argument 

msg['Subject'] = "Auto Hella Restart Report "sys.argv[1]  #line where i am using that passed argument

回答1:

I'm guessing that you meant to do this:

msg['Subject'] = "Auto Hella Restart Report " + sys.argv[1]
# To concatenate strings in python, use       ^ 

回答2:

Try:

msg['Subject'] = "Auto Hella Restart Report " + sys.argv[1]

The + operator is overridden in python to concatenate strings.

回答3:

If you need to add two strings you have to use the '+' operator

hence

msg['Subject'] = your string + sys.argv[1]

and also you have to import sys in the begining

as

import sys

msg['Subject'] = "Auto Hella Restart Report " + sys.argv[1]

回答4:

variable=" Hello..."  
print (variable)  
print("This is the Test File "+variable)  

for integer type ...

variable="  10"  
print (variable)  
print("This is the Test File "+str(variable))  

回答5:

I know this is a little old but I wanted to add an updated answer with f-strings which were introduced in Python version 3.6:

msg['Subject'] = f'Auto Hella Restart Report {sys.argv[1]}'

回答6:

With python 3.6+:

msg['Subject'] = f"Auto Hella Restart Report {sys.argv[1]}"

来源：https://stackoverflow.com/questions/18348717/how-to-use-concatenate-a-fixed-string-and-a-variable-in-python