Exercise 22 - Python Words & Symbols Flashcards
print ‘string’
Prints a string
print “string”
Prints a string
#
(Octothorpe) - starts a comment
+
(Plus) - adds
-
(Minus) - subtracts
/
(Slash) - divides
*
(Asterisk) - multiplies
%
(Percent sign) - mod or modulus function
<
Less than - compares two values or strings, returns True or False
>
Greater than - compares two values or strings, returns True or False
<=
Less than equal - compares two values or strings, returns True or False
> =
Greater than equal - compares two values or strings, returns True or False
=
Assigns a value or string to a variable, I.e., var = “ text” or var = 3
,
Comma, separates lists of things
%s
Format character, string
%d
Format character, number
%r
Format character, returns input, I.e., raw contents of the variable = ‘representation’
% var
Places var in formatter location
% (var1, var2, var3)
Places vars in multiple formatter locations
3.0, for example
Appending .0 to the 3 results in floating point math operations
round()
Rounds a floating point number
False
Logical false
True
Logical true
- used with a string
Repeats a string char, I.e., print “.” * 10 results in ……….
+ used with strings
Concatenates the strings in the print function
, used with print
Removes the line feed at the end of print, I.e., print "Mary", print "lamb" Results in: Mary lamb
\
(Backslash) - escape character
print “"”…”””
print ‘'’…’’’
Triple quotes allow printing of lines as typed
raw_input( )
Prompts user for a string or a value, outputs a string
int(raw_input( ))
Converts string to a number
Input( )
Converts entry as if it is python code; security issues, don’t use
raw_input(“string”)
Prompts for input by printing “string”
pydoc
Terminal command that prints python documentation, I.e., pydoc raw_input() prints doc for raw_input()
From sys import argv
Imports function argv from sys (sys is a package)
argv
Packs arguments given to a program; first one is the function (script) name
module
Another name for a function or feature
Prompt
”> “ is one, I.e., raw_input(“> “)
var = raw_input(“> “)
Passes user input to var
var = open(filename)
Opens the file “filename” and passes file object to var
var.read()
Reads the contents of var if var is file info, e.g.:
var = open(filename)
print var.read()
Prints contents of filename as contained in var
close()
closes the file, e.g.:
var = open(filename)
...
....
var.close().close()
Close the file
.read()
Read the file
.readline()
Read one line of a text file
.truncate()
Empty the file
.write(stuff)
Writes stuff to the file
Open(filename, ‘w’)
Opens filename and allows writing to the file. Can use:
‘w’ write, ‘r’ read, ‘a’ append
Default is read, so ‘r’ can be omitted
from os.path import exists
Imports exists module
exists(filename)
Returns True if filename exists, else False
This is the exists module
cat
Concatenation, Linux command
cat filename prints the contents of filename
len(string)
Outputs the character count of a string as a number
def
defines a function
def print_two(*args):
arg1, arg2 = args
print "arg1: %r, arg2: %r" % (arg1, arg2).seek(0)
Rewinds a .read() of a file
+= n
Increments a variable by n
var += 2 is equivalent to var = var + 2
return
Returns a value from a function
def add(a, b)
return a + b
Executing var = add(3, 4) places 7 in var
