Python -- file and exception

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Reading data from a file

function open() Take a parameter ： The name of the file to open . then Python The specified file will be found in the directory where the currently executed file is located , function open() Returns an object representing a file .

1. Read entire file

with open(" File name ") as file_object:
    contents = file_object.read()
print(contents)
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function open() In parentheses , The input file name is limited to the file stored in the directory of the currently executed file , If the file is not in the current directory , Enter the file path .

2. Read line by line

filename = "name.txt"
with open(filename) as file_object:
    for line in file_object:
        print(line.rstrip())
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rstrip() Used to eliminate redundant blank lines

3. write file

filename = "name.txt"
with open(filename,'w') as file_object:
    file_object.write(" Write content ")
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function open() Provide 7 Basic opening method

abnormal

try-except sentence

try:
    < Sentence block 1>
except < exception handling >:
    < Sentence block 2>
……
except < Exception types N>:
    < Sentence block N+1>
except:
    < Sentence block N+2>
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If try The code in the block runs without problems ,python Will skip except Code block ; If try The code in the code block caused the error ,python Will find a match except Code block and run the code in it . such , The user will see a friendly error message , instead of traceback.

Exception statements can also be associated with else and finally Use with reserved words

try:
    < Sentence block 1>
except < Exception types 1>:
    < Sentence block 2>
else:
    < Sentence block 3>
finally:
    < Sentence block 4>,
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