wrapped. (If a file descriptor is given, it is closed when the

returned I/O object is closed, unless closefd is set to False.)


mode is an optional string that specifies the mode in which the file

is opened. It defaults to 'r' which means open for reading in text

mode. Other common values are 'w' for writing (truncating the file if

it already exists), 'x' for creating and writing to a new file, and

'a' for appending (which on some Unix systems, means that all writes

append to the end of the file regardless of the current seek position).

In text mode, if encoding is not specified the encoding used is platform

dependent: locale.getpreferredencoding(False) is called to get the

current locale encoding. (For reading and writing raw bytes use binary

mode and leave encoding unspecified.) The available modes are:


========= ===============================================================

Character Meaning

--------- ---------------------------------------------------------------

'r' open for reading (default)

'w' open for writing, truncating the file first

'x' create a new file and open it for writing

'a' open for writing, appending to the end of the file if it exists

'b' binary mode

't' text mode (default)

'+' open a disk file for updating (reading and writing)

'U' universal newline mode (deprecated)

========= ===============================================================


The default mode is 'rt' (open for reading text). For binary random

access, the mode 'w+b' opens and truncates the file to 0 bytes, while

'r+b' opens the file without truncation. The 'x' mode implies 'w' and

raises an `FileExistsError` if the file already exists.


Python distinguishes between files opened in binary and text modes,

even when the underlying operating system doesn't. Files opened in

binary mode (appending 'b' to the mode argument) return contents as

bytes objects without any decoding. In text mode (the default, or when

't' is appended to the mode argument), the contents of the file are

returned as strings, the bytes having been first decoded using a

platform-dependent encoding or using the specified encoding if given.


'U' mode is deprecated and will raise an exception in future versions

of Python. It has no effect in Python 3. Use newline to control

universal newlines mode.


buffering is an optional integer used to set the buffering policy.

Pass 0 to switch buffering off (only allowed in binary mode), 1 to select

line buffering (only usable in text mode), and an integer > 1 to indicate

the size of a fixed-size chunk buffer. When no buffering argument is

given, the default buffering policy works as follows:


* Binary files are buffered in fixed-size chunks; the size of the buffer

is chosen using a heuristic trying to determine the underlying device's

"block size" and falling back on `io.DEFAULT_BUFFER_SIZE`.

On many systems, the buffer will typically be 4096 or 8192 bytes long.


* "Interactive" text files (files for which isatty() returns True)

use line buffering. Other text files use the policy described above

for binary files.


encoding is the name of the encoding used to decode or encode the

file. This should only be used in text mode. The default encoding is

platform dependent, but any encoding supported by Python can be

passed. See the codecs module for the list of supported encodings.


errors is an optional string that specifies how encoding errors are to

be handled---this argument should not be used in binary mode. Pass

'strict' to raise a ValueError exception if there is an encoding error

(the default of None has the same effect), or pass 'ignore' to ignore

errors. (Note that ignoring encoding errors can lead to data loss.)

See the documentation for codecs.register or run 'help(codecs.Codec)'

for a list of the permitted encoding error strings.


newline controls how universal newlines works (it only applies to text

mode). It can be None, '', '\n', '\r', and '\r\n'. It works as

follows:


* On input, if newline is None, universal newlines mode is

enabled. Lines in the input can end in '\n', '\r', or '\r\n', and

these are translated into '\n' before being returned to the

caller. If it is '', universal newline mode is enabled, but line

endings are returned to the caller untranslated. If it has any of

the other legal values, input lines are only terminated by the given

string, and the line ending is returned to the caller untranslated.


* On output, if newline is None, any '\n' characters written are

translated to the system default line separator, os.linesep. If

newline is '' or '\n', no translation takes place. If newline is any

of the other legal values, any '\n' characters written are translated

to the given string.


If closefd is False, the underlying file descriptor will be kept open

when the file is closed. This does not work when a file name is given

and must be True in that case.


A custom opener can be used by passing a callable as *opener*. The

underlying file descriptor for the file object is then obtained by

calling *opener* with (*file*, *flags*). *opener* must return an open

file descriptor (passing os.open as *opener* results in functionality

similar to passing None).


open() returns a file object whose type depends on the mode, and

through which the standard file operations such as reading and writing

are performed. When open() is used to open a file in a text mode ('w',

'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open

a file in a binary mode, the returned class varies: in read binary

mode, it returns a BufferedReader; in write binary and append binary

modes, it returns a BufferedWriter, and in read/write mode, it returns

a BufferedRandom.


It is also possible to use a string or bytearray as a file for both

reading and writing. For strings StringIO can be used like a file

opened in a text mode, and for bytes a BytesIO can be used like a file

opened in a binary mode.



In [90]: fr = open("first.txt", "r")


In [91]: type(fr)

Out[91]: _io.TextIOWrapper


In [92]: mydata = fr.readlines()


In [93]: fr.close()


In [94]: mydata

Out[94]: ['Hello World']


In [95]: fr = open("first.txt", "r")


In [96]: mydata = fr.readlines()


In [97]: fr.close()


In [98]: mydata

Out[98]:

['Hello World\n',

'Today is tuesday\n',

'This is another line\n',

'and yyet another line']


In [99]: len(mydata)

Out[99]: 4


In [100]: mydata[2]

Out[100]: 'This is another line\n'


In [101]: fr = open("first.txt", "r")


In [102]: mydata1 = fr.read()


In [103]: fr.close()


In [104]: mydata

Out[104]:

['Hello World\n',

'Today is tuesday\n',

'This is another line\n',

'and yyet another line']


In [105]: mydata1

Out[105]: 'Hello World\nToday is tuesday\nThis is another line\nand yyet another line'


In [106]: mydata1.split()

Out[106]:

['Hello',

'World',

'Today',

'is',

'tuesday',

'This',

'is',

'another',

'line',

'and',

'yyet',

'another',

'line']


In [107]: for i in mydata1.split():

     ...: i.upper()

     ...:


In [108]: for i in mydata1.split():

     ...: print(i.upper())

     ...:

HELLO

WORLD

TODAY

IS

TUESDAY

THIS

IS

ANOTHER

LINE

AND

YYET

ANOTHER

LINE


In [109]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/Lecture4b.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line


In [110]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/Lecture4b.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line

Hello World


Today is tuesday


This is another line


and yyet another line


In [111]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/Lecture4b.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line


Hello World


Today is tuesday


This is another line


and yyet another line


In [112]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/Lecture4b.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line


['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


In [113]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/Lecture4b.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line


['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


In [114]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/Lecture4b.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line


['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']

Hello World

Today is tuesday

This is another line

and yyet another line


In [115]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/Lecture4b.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line


['Hello World\n', 'Today is tuesday\n', 'This is another line\n', 'and yyet another line']


Hello World

Today is tuesday

This is another line

and yyet another line


In [116]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [117]: total_cost("shoppinglist.txt")

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

['bread', '5', '1.39']

6.949999999999999

6.949999999999999 £

['tomatoes', '6', '0.26']

1.56

1.56 £

['milk', '3', '1.45']

4.35

4.35 £

['coffee', '3', '2.99']

8.97

8.97 £

['beer', '50', '1.10']

55.00000000000001

55.00000000000001 £

Out[117]: 76.83000000000001


In [118]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [119]: total_cost("shoppinglist.txt")

6.949999999999999 £

1.56 £

4.35 £

8.97 £

55.00000000000001 £

Out[119]: 76.83000000000001


In [120]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [121]: total_cost("shoppinglist.txt")

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

6.949999999999999 £

1.56 £

4.35 £

8.97 £

55.00000000000001 £

Out[121]: 76.83000000000001


In [122]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [123]: total_cost("shoppinglist.txt")

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

['bread', '5', '1.39']

6.949999999999999 £

['tomatoes', '6', '0.26']

1.56 £

['milk', '3', '1.45']

4.35 £

['coffee', '3', '2.99']

8.97 £

['beer', '50', '1.10']

55.00000000000001 £

Out[123]: 76.83000000000001


In [124]: '1'+'1'

Out[124]: '11'


In [125]: float('1')+float('1')

Out[125]: 2.0


In [126]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [127]: total_cost("shoppinglist.txt")

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

['bread', '5', '1.39']

6.949999999999999

6.949999999999999 £

['tomatoes', '6', '0.26']

1.56

1.56 £

['milk', '3', '1.45']

4.35

4.35 £

['coffee', '3', '2.99']

8.97

8.97 £

['beer', '50', '1.10']

55.00000000000001

55.00000000000001 £

Out[127]: 76.83000000000001


In [128]: "W"

Out[128]: 'W'


In [129]: ord("W")

Out[129]: 87


In [130]: ord("w")

Out[130]: 119


In [131]: chr(119)

Out[131]: 'w'


In [132]: chr(163)

Out[132]: '£'


In [133]: chr(36)

Out[133]: '$'


In [134]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [135]: total_cost("shoppinglist.txt")

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

['bread', '5', '1.39']

6.949999999999999

6.949999999999999 £

['tomatoes', '6', '0.26']

1.56

1.56 £

['milk', '3', '1.45']

4.35

4.35 £

['coffee', '3', '2.99']

8.97

8.97 £

['beer', '50', '1.10']

55.00000000000001

55.00000000000001 £

Out[135]: 76.83000000000001


In [136]: total_cost(shoppinglist.txt)

Traceback (most recent call last):


File "<ipython-input-136-f46b6e6b772b>", line 1, in <module>

total_cost(shoppinglist.txt)


NameError: name 'shoppinglist' is not defined



In [137]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')

File "//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py", line 3

def total_cost(str(shoplist_file)):

^

SyntaxError: invalid syntax



In [138]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [139]: total_cost(shoppinglist.txt)

Traceback (most recent call last):


File "<ipython-input-139-f46b6e6b772b>", line 1, in <module>

total_cost(shoppinglist.txt)


NameError: name 'shoppinglist' is not defined



In [140]: total_cost("shoppinglist.txt")

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

['bread', '5', '1.39']

6.949999999999999

6.949999999999999 £

['tomatoes', '6', '0.26']

1.56

1.56 £

['milk', '3', '1.45']

4.35

4.35 £

['coffee', '3', '2.99']

8.97

8.97 £

['beer', '50', '1.10']

55.00000000000001

55.00000000000001 £

Out[140]: 76.83000000000001


In [141]: a = "shoppinglist.txt"


In [142]: total_cost(a)

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

['bread', '5', '1.39']

6.949999999999999

6.949999999999999 £

['tomatoes', '6', '0.26']

1.56

1.56 £

['milk', '3', '1.45']

4.35

4.35 £

['coffee', '3', '2.99']

8.97

8.97 £

['beer', '50', '1.10']

55.00000000000001

55.00000000000001 £

Out[142]: 76.83000000000001


In [143]: runfile('//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4/lecture4_read.py', wdir='//filestore.soton.ac.uk/users/oh1m12/mydocuments/20172018/Lecture4')


In [144]: total_cost("shoppinglist.txt")

['bread 5 1.39\n', 'tomatoes 6 0.26\n', 'milk 3 1.45\n', 'coffee 3 2.99\n', 'beer 50 1.10']

['bread', '5', '1.39']

6.949999999999999

6.949999999999999 £

['tomatoes', '6', '0.26']

1.56

1.56 £

['milk', '3', '1.45']

4.35

4.35 £

['coffee', '3', '2.99']

8.97

8.97 £

['beer', '50', '1.10']

55.00000000000001

55.00000000000001 £

Out[144]: 76.83000000000001


In [145]: