Loops are a common tool used in Python to help users iterate through lists, or perform the same operation numerous times without added efforts.
Let’s look at a few examples:
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| # Loops
for n in [0, 1, 5, 2, -5]:
# this is inside the loop
print("The number is", n, "and its squared value is", n**2)
# this is outside the loop
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| ## The number is 0 and its squared value is 0
## The number is 1 and its squared value is 1
## The number is 5 and its squared value is 25
## The number is 2 and its squared value is 4
## The number is -5 and its squared value is 25
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| ## Loop
s = "Python"
for c in s:
print(c + "!")
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| ## P!
## y!
## t!
## h!
## o!
## n!
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| # range(10) sets values 0-9, because recall Python starts at 0, not 1
for i in range(10):
print(i)
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| ## 0
## 1
## 2
## 3
## 4
## 5
## 6
## 7
## 8
## 9
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This is equivalent to writing:
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| for i in range(0,10):
print(i)
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| ## 0
## 1
## 2
## 3
## 4
## 5
## 6
## 7
## 8
## 9
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If we wanted it to start at 1 and go to 10 (inclusive), we would write:
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| for i in range(1,11):
print(i)
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| ## 1
## 2
## 3
## 4
## 5
## 6
## 7
## 8
## 9
## 10
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Other examples:
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| #(start,end,increments)
for i in range(0,101,10):
print(i)
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| ## 0
## 10
## 20
## 30
## 40
## 50
## 60
## 70
## 80
## 90
## 100
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| n = 3
while n > 0:
print(n)
n = n - 1
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