from:http://interactivepython.org/courselib/static/pythonds/Introduction/InputandOutput.html
Input and Output
- Input
Python’s input function takes a single parameter that is a string. This string is often called the prompt because it contains some helpful text prompting the user to enter something. For example, you might call input as follows:
aName = input('Please enter your name: ')
aName = input("Please enter your name ")
print("Your name in all capitals is",aName.upper(),
"and has length", len(aName))
It is important to note that the value returned from the input
function will be a string representing the exact characters that were entered after the prompt. If you want this string interpreted as another type, you must provide the type conversion explicitly.
sradius = input("Please enter the radius of the circle ")
radius = float(sradius)
diameter = 2 * radius
-
Output (String Formatting)
>>> print("Hello") Hello >>> print("Hello","World") Hello World >>> print("Hello","World", sep="***") Hello***World >>> print("Hello","World", end="***") Hello World***
>>>print(aName, "is", age, "years old.")
>>>print("%s is %d years old." % (aName, age))
The%
operator is a string operator called the format operator.
Character | Output Format |
---|---|
d , i |
Integer |
u |
Unsigned integer |
f |
Floating point as m.ddddd |
e |
Floating point as m.ddddde+/-xx |
E |
Floating point as m.dddddE+/-xx |
g |
Use %e for exponents less than −4 −4 or greater than +5 +5 , otherwise use %f |
c |
Single character |
s |
String, or any Python data object that can be converted to a string by using the str function. |
% |
Insert a literal % character |
In addition to the format character, you can also include a format modifier between the %
and the format character. Format modifiers may be used to left-justify or right-justifiy the value with a specified field width.
Modifier | Example | Description |
---|---|---|
number | %20d |
Put the value in a field width of 20 |
- |
%-20d |
Put the value in a field 20 characters wide, left-justified |
+ |
%+20d |
Put the value in a field 20 characters wide, right-justified |
0 |
%020d |
Put the value in a field 20 characters wide, fill in with leading zeros. |
. |
%20.2f |
Put the value in a field 20 characters wide with 2 characters to the right of the decimal point. |
(name) |
%(name)d |
Get the value from the supplied dictionary using name as the key. |
>>> price = 24
>>> item = "banana"
>>> print("The %s costs %d cents"%(item,price))
The banana costs 24 cents
>>> print("The %+10s costs %5.2f cents"%(item,price))
The banana costs 24.00 cents
>>> print("The %+10s costs %10.2f cents"%(item,price))
The banana costs 24.00 cents
>>> itemdict = {"item":"banana","cost":24}
>>> print("The %(item)s costs %(cost)7.1f cents"%itemdict)
The banana costs 24.0 cents
>>>
In addition to format strings that use format characters and format modifiers, Python strings also include a format
method that can be used in conjunction with a new Formatter
class to implement complex string formatting. More about these features can be found in the Python library reference manual.