Continuing a Statement on One or More Lines
The backslash character \ is the line continuation character, and allows you to continue a Python statement on the next line.
>>> sum = 2.35 + 8 \
... + 13.6 + \
>>> print "\t\nHello, my name is", \
Hello, my name is Jarvis
The string formatting operator %
We use the formatting operator % to indicate how a number should be displayed.
General form: print format_string % number
>>> import math # this package contains a constant for the value of pi
>>> math.pi # display the value of pi
>>> # Now we display pi with 4 digits after the decimal point
>>>print "Pi with 4 digits after the decimal point: %.4f" % math.pi
Pi with 4 digits after the decimal point: 3.1416
1. the f in the format string means that we are printing a float.
2. The number (in this example, math.pi) appears in the output wherever the format string occurs.
3. The number is rounded to the specified number of digits.
We can also specify a minimum field width for the display of the number. The minimum width comes before the decimal point in the format string.
>>> print "Pi = %7.3f" % math.pi
Pi = 3.142
The width of the field is 7, and the numbers and decimal point have
width 5, so there are 2 blank spaces to the left of the number.
Here are the characters that you use with % in the format string to indicate different types:
s - string
e - exponential format for a floating point number (with lowercase e)
E - exponential format (with uppercase E)
d - integer
>>> print "%.3E" % math.pi
>>> print "%.3e" % math.pi
>>> print "%15s" % "hello"
>>> print "My favorite number %5d is cool!" % 13
My favorite number 13 is cool!
Using format strings to display multiple values
When you are formatting two or more values in a print statement,
enclose the values in parentheses, and separate the values with
>>> print "My first name is %10s and my last name is %12s" % ("Elvis", "Presley")
My first name is Elvis and my last name is Presley
"Once you make a decision, the universe conspires to make it happen."
--- Ralph Waldo Emerson
The if statement
The if statement executes its block (one or more statements) only when its condition is true.
>>> number = 25
>>> if number > 10:
. . . print number, "is greater than 10!"
. . .
25 is greater than 10!
|| What it means
|| greater than
|| less than
|| greater or equal
|| less than or equal
Note: In Python, we can compare strings with these operators:
"elvis" < "jasper" since elvis comes before "jasper" in alphabetical order. More on this later...
num1 = 10
num2 = 5
if num2 < num1:
print num2, "is less than", num1
if num1 != num2:
print num1, "is not equal to", num2
if num1 == num2:
print num1, "is equal to", num2
5 is less than 10
10 is not equal to 5
The if-else statement
An if-else statement executes one of two blocks of statements. One
block is executed if the if statement's condition is true, and the
other is executed if the condition is false.
Exercise: Write a program that
asks the user to enter a number. If the number is 3, print a message
indicating that they entered your favorite number, and otherwise,
indicate that you don't like the chosen number.
The if-elif-else statement
The if-elif-else statement executes exactly one of several blocks, depending on which of several conditions is true.
Note: You may use as many elif
clauses as you like. The conditions are executed in order - condition1,
condition2, etc. - until a true condition is found, and the block for
that true condition is executed. If none of the conditions are true,
the else block is executed.
number = input("Please enter your number: ")
if number < 10:
print number, "is small"
elif number < 100:
print number, "is pretty big"
elif number < 500:
print number, "is big"
print "Wow, a really big number!"
Please enter your number: 355
355 is big
Exercise: Write a program that
asks the user for the current month and the current day, and then
prints the month and day in mm/dd format.