Python basics: conditions and iterations

Next is about conditions and repetition

if statement

Meaning in Japanese It ’s a pretty important position in programming.

#format
if #First condition

elif #Second to n conditions

else #Other than the nth condition

#Example of use
#After the condition ":Don't forget to indent the output

n = 3
if n == 1: 
    print("No. 1 processing") 
elif n == 2:
    print("No. 2 processing") 
elif n == 3: 
    print("No. 3 processing") 
else: #When all the above conditional expressions are not satisfied
    print("Processing other than the above")

#output:No. 3 processing

Comparison operator

True if basic conditions are met If it does not come out, falsa is returned.

Boolean operator (and ・ or ・ not)

A and B #Conditional expressions for both A and B are satisfied
A or B #Either A or B conditional expression is satisfied
not conditional expression#Result reversal

Example of use

A = 1
B = 2

print(A==1 and B==2)
# true
 
print(not B < A)
# true

while statement

Processing that repeats while the condition is met

while

n = 5
while n >2: #If n is greater than 0, perform the following processing
    print(n)
    n -= 2 #n-1

#Output result 5 3

while + if statement

x = 5
while x != 0:
    x -= 1
    if x != 0:
        print(x)
    else:
        print("end")

for statement

I will post more about the list later We will go through the contents of multiple variables.

moji = ["A", "B", "C"]
for ji in moji: #Number of elements contained in animals = Repeat processing 3 times
    print(ji)
#Output result
A
B
C

break End of repetition

break

li = [1, 2, 3]
for n in li:
    print(n)
    if n >= 3: 
        print("Confirm 3 or more")
        break #end of for statement processing

continue Used when you want to skip processing

continue

li = [10, 20, 30, 40] #Number of elements contained in storages=Repeat processing 6 times
for n in li:
    if n < 30: #If n is less than 30, no processing is performed(skip)
        continue
    print(n)

#Output result
3
4

Repeated application

There is also a repeat method that mixes index and key and value.

Repeat with index

It is used when you want to display the index in the for statement.

index display

li = ["iti", "ni"]
for index, value in enumerate(li):
    print(index, value)
#Output result
0 a
1 b

Repeating multiple lists

It can be output by preparing the variable of the assignment destination.

Repeating multiple lists

li = [[1, 2, 3], [4, 5, 6]]
for a, b, c in li:
    print(a, b, c)
#Output result
1 2 3
4 5 6

However, if the original data does not contain the number statement data, an error will occur.

Multiple list repetition error

li = [[1, 2, 3], [4, 5]]
for a, b, c in li:
    print(a, b, c) #Get an error
#Output result
not enough values to unpack (expected 3, got 2)

Dictionary-type repetition

By using a function called items () You can use both keys and values.

Dictionary-style repetition

man = {"name": "yamada", "hair": "black", "arm": "left"}
for hidari, migi in man.items(): 
#The key is stored in hidari and the value is stored in migi.
        print(hidari+" is "+migi)

#Output result
name is yamada
hair is black
arm is left