for loops can be used to step through lists, tuples, and other ’iterable’ objects.
Iterating through a list:
for item in [10,25,50,75,100]:
print (item, item**2)
OUT:
10 100
25 625
50 2500
75 5625
100 10000
A for loop may be used to generate and loop through a sequence of numbers (note that a ’range’ does not include the maximum value specified):
for i in range(100,150,10):
print(i)
OUT:
100
110
120
130
140
A for loop may be used to loop through an index of positions in a list:
my_list = ['Frodo','Bilbo','Gandalf','Gimli','Sauron']
for i in range(len(my_list)):
print ('Index:',i,', Value',my_list[i])
OUT:
Index: 0 , Value Frodo
Index: 1 , Value Bilbo
Index: 2 , Value Gandalf
Index: 3 , Value Gimli
Index: 4 , Value Sauron
Breaking out of loops or continuing the loop without action
Though it may not be considered best coding practice, it is possible to prematurely escape a loop with the break command:
for i in range(10): # This loop would normally go from 0 to 9
if i == 5:
break
else:
print(i)
print ('Loop complete')
OUT:
0
1
2
3
4
Loop complete
Or, rather than breaking out of a loop, it is possible to effectively skip an iteration of a loop with the continue command. This may be places anywhere in the loop and returns the focus to the start of the loop.
for i in range (10):
if i%2 == 0: # This is the integer remainder after dividing i by 2
continue
else:
print (i)
print ('Loop complete')
OUT:
1
3
5
7
9
Loop complete
Using pass to replace active code in a loop
The pass command is most useful as a place holder to allow a loop to be built and have contents added later.
for i in range (10):
# Some code will be added here later
pass
print ('Loop complete')
OUT:
Loop complete
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