I have a python code ,i need to get its value outside the for loop and if statements and use the variable further:
My code:
with open('text','r') as f:
for line in f.readlines():
if 'hi' in line
a='hello'
print a #variable requires outside the loop
But i get Nameerror: 'a' is not defined
The error message means you never assigned to a (i.e. the if condition never evaluated to True).
To handle this more gracefully, you should assign a default value to a before the loop:
a = None
with open('test', 'r') as f:
...
You can then check if it's None after the loop:
if a is not None:
...
You may also try:
try:
print a
except NameError:
print 'Failed to set "a"'
EDIT: It simultaneously solves the problem of not printing a , if you did not find what you were looking for
The other answers here are correct—you need to guarantee that a has been assigned a value before you try to print it. However, none of the other answers mentioned Python's for ... else construct, which I think is exactly what you need here:
with open('text','r') as f:
for line in f.readlines():
if 'hi' in line:
a='hello'
break
else:
a='value not found'
print a #variable requires outside the loop
The else clause is only run if the for loop finishes its last iteration without break-ing.
This construct seems unique to Python in my experience. It can be easily implemented in languages that support goto, but Python is the only language I know of with a built-in construct specifically for this. If you know of another such language, please leave a comment and enlighten me!
just define a=null or a=0
so a become global variable and you can access a in anywhere in your code
aoutside the loopais not guaranteed to be set by the code.