ESCI 386 Scientific Programming, Analysis and ...
嚜激SCI 386 每 Scientific Programming,
Analysis and Visualization with
Python
Lesson 6 - File IO
1
Opening/Closing Files
? A file is opened for reading using the open statement
f = open(file_name, &r*)
每 This returns a file object, in this case named f. We
could have named it whatever we wanted.
每 The &r* specifies the mode of the file be read only.
每 The different possible modes are
Mode
Meaning
Mode
Meaning
&r*
Read only (text file)
&rb*
Read only (binary file)
&w*
Write only (text file)
&wb*
Write only (binary file)
&r+* or
&w+*
Read and write (text file)
&rb+* or
&wb+*
Read and write (binary file)
&a*
Append (text file)
&ab*
Append (binary file)
2
Opening/Closing Files
?
An ASCII file is opened for reading using the open statement
f = open(file_name, &r*)
每 This returns a file object, in this case named f. We could have named it
whatever we wanted.
每 The &r* specifies the mode of the file be read only.
每 To open a file for writing we would use &w* instead of &r*.
每 Opening a file with &a* will open the file for writing and append data to the
end of the file.
每 To open a file for both reading and writing we use either &r+* or &w+*.
?
You should always close a file when you are done with it. This is done with
f.close()
3
Automatically Closing Files
? Python has a shorthand for opening a file, manipulating its
contents, and then automatically closing it.
? The syntax is
with open(filename, &r*) as f:
[code statements within code block]
? This opens the file and gives the file object the name f.
? The file will automatically close when the code block
completes, without having to explicitely close it.
4
Interactive File Selection
? The code below allows interactive selection of
file names.
import Tkinter as tk
from tkFileDialog import askopenfilename as pickfile
window = tk.Tk() # Create a window
window.withdraw() # Hide the window
filename = pickfile(multiple=False)
window.quit() # quit the window
5
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