Python file handling - readingยง
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Also see the [[Programming Main Page]] or the [[Main AI Page]]
For code examples see [[Week4 Reading From Files Lab]]
See [[Python file handling - writing]]
The ‘open()’ functionยง
Syntax:
File1 = open("/home/websinthe/Documents/code/example.txt", "r")
- File1 <— File object
- open <— function name
- "/home/websinthe/…/example.txt" <— file path
- "r" <— mode
Common modes include:
- w <— write (writes from beginning of file)
- r <— read
- a <— append
- r+ <— read/write (need to take care of line cursor placement)
- x <— create file
You use the file object to gain information about the file. Think of it as pouring the contents of the file into a variable and using the variable’s methods to interact with the file’s data.
File1.name —> /home/websinthe/Documents/code/example.txt
File1.mode —> r
File1.close —> you always need to close the file, which is why you always use the with statement instead of just opening a file straight up.
The ‘with’ context managerยง
#contextmanager
The with context manager ensures that the file being manipulated is closed after it is used without the code having to explicitly handle the file’s closure.
with open("/home/websinthe/Documents/code/example.txt", "r") as File1:
file_contents = File1.read()
print(file_contents)
All operations within the indent block will be executed and then the file will be closed.
file_contents = File1.read() <— outputs the contents of the file to the variable
file_contents = File1.readlines() <— outputs the lines of the file as elements of a list object to the variable
file_contents = File1.readline() <— outputs the first line of the file to the variable, ==each subsequent time it is called, it will output the next line to the variable==
file_contents = File1.readlines(4) <— outputs the first 4 characters of each line to the variable
