Created
March 20, 2024 11:39
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An example of context managers allocating and releasing resources precisely
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# requirement: create the txt file: zen_of_python.txt in the same directory that this python file | |
filename = 'zen_of_python.txt' | |
f = open(filename, 'r') | |
print("1st option 2 print content file") | |
print(f.read()) | |
f.close() | |
# two related operations which you’d like to execute as a pair, with a | |
# block of code in between. | |
open_file = open(filename, 'r') | |
with open_file: | |
print("2nd option 2 print content file") | |
print(open_file.read()) | |
""" | |
with EXPRESSION as TARGET: | |
SUITE | |
@see: https://docs.python.org/3/reference/compound_stmts.html#the-with-statement | |
unhandled error | |
""" | |
with open(filename) as open_file: | |
print("3rd option 2 print content file") | |
""" | |
for line in open_file: | |
print(line.rstrip()) | |
""" | |
print(open_file.read()) | |
# The final solution, handling exceptions | |
class File(object): | |
def __init__(self, file_name, method): | |
try: | |
self.file_obj = open(file_name, method) | |
except Exception as e: | |
print(f"Exception: {e}") | |
def __enter__(self): | |
return self.file_obj | |
def __exit__(self, type, value, traceback): | |
if type: | |
print(f"Exception of type: {type} has been handled: {value}") | |
self.file_obj.close() | |
return True | |
with File('zen_of_python.txt', 'r') as open_file: | |
# Exception here are managed in File.__exit__ | |
print("4th option 2 print content file") | |
print(open_file.read()) |
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