for-loops.md

For Loops

Basic for loops

• Let us do the same thing for a number of different values

for item in list_of_items:
    commands

pets = ['spot', 'gigantor', 'fluffy']
for pet in pets:
    print "%s is the name of a class pet" % pet

Lists

• lists hold multiple values of any type
• have methods to let us manipulate them
  • e.g., insert, append
• these methods return None, different from string methods

Using loops with append

• a common thing to do with a loop is to do some calculations and store the resulting value
• the simplest way to do this is using a list and .append()

results = []
for name in pets:
    capitalized_name = name.upper()
	results.append(capitalized_name)
print results

• a common mistake is to forget that list methods work "in-place"

results = []
for name in pets:
    capitalized_name = name.upper()
	results = results.append(capitalized_name)
print results