Files in jython

Files

File objects are handled with built-in functions. The open method is used to open a file for reading or writing operations.

The following table shows the most common methods used for files

F

Operation	Description
f = open(filename [, mode='r'])	Opens a file in the proper mode: mode : 'r' : Read 'w' : Write. Create the file if it does not exist 'a' : Append. '+' : (added to the previous modes - example 'a+') opens the file for updates 'b' : (added to the previous modes - example 'rb') open the file in binary mode
f.close()	Closes the f file
f.fileno()	Returns descriptor of the f file
f.flush()	Empties the internal buffer of f
f.isatty()	Returns true if f is a TTY
f.read([size])	Reads a maximum of size bytes from the file and returns a string
f.readline()	Reads a line from f
f.readlines()	Reads until the end of file (EOF) and returns a list of lines
f.xreadlines()	Returns a sequence without reading until the end of file (preferred to readlines()
f.seek(offset[, whence=0])	Sets the file's current position to 'offset' bytes from 'whence': 0: from the beginning of the file 1: from the current location 2: from the end of the file
f.tell()	Returns the current location in the file
f.write(str)	Writes str into the file
f.writelines(list)	Writes a list of strings in the file

Tuples in jython

Tuples

Tuples are non modifiable object arrays parsed with an index.
A tuple is handled as a series of values separated by commas and within brackets.

·         () is an empty tuple

·         (0,1,2,3) is a 4 elements tuple, indexed from 0 to 3

·         tuple = (0, (1, 2), (4,5,6)) is a tuple that contains other tuples. tuple[1][0] returns 1

Operations on sequences are available for the tuples.

Some methods to handle dictionaries in jython

Some methods to handle dictionaries

Method	Description
adict.has_key(k)	Returns TRUE (1) if the key k exists in the dictionary
adict.keys()	Returns the list of dictionary keys
adict.values()	Returns a list of dictionary values
adict.items()	Returns a list of tuples (key, value) for each element of the dictionary
adict.clear()	Deletes all elements of adict
adict.copy()	Returns a copy of adict
dic1.update(dic2)	Update the dictionary dic1 with the values of dic2  based on the values of the keys
adict.get(k[,default])	Equivalent to adict[k] but returns default if k cannot be found.
adict.popitem()	Retrieves an element and deletes it from the dictionary

Dictionaries in jython

Dictionaries

Dictionaries are arrays of objects indexed on a key (string value) and not by an index.
A dictionary is accessed with a tuple key:value separated by commas and in brackets.

·         {} is an empty dictionary

·         {'P1':'Watch', 'P2': 'Birds', 'P3':'Horses'} is a dictionary with 3 elements with the following keys: P1, P2 and P3

·         adict = {'FR_US':{'Bonjour':'Hello', 'Au revoir':'Goodbye'}, 'US_FR':{'Hello': 'Bonjour','Goodbye':'Au Revoir'}} is a dictionary that contains other dictionaries. To translate 'Hello' in French:: adict['US_FR']['Hello']

Some list functions in jython

Some list functions

Method	Description
mylist.append(x)	Adds an element at the end of the list
mylist.sort([function])	Sorts the list with the optional [function] comparison function
mylist.reverse()	Reverses the list (from last to first)
mylist.index(x)	Seeks the index x
mylist.insert(i, x)	Inserts x at index i
mylist.count(x)	Returns the number of occurrences of x in the list
mylist.remove(x)	Deletes the first occurrence of x in the list
mylist.pop([i])	Deletes and return the last element in the list or the element at index i