For in Python Loop

This guide covers for in python loop with practical context and easy-to-follow details. Use it to understand the subject and apply the information confidently.

In the previous section we learned quite a bit about the if statement in Python. Read this article to make sure you don't miss out on useful information about it.

Syntax for for in Python

for bien_lap in chuoi_lap:
 Kh?i l?nh c?a for

In the above syntax, chuoi_lap is the string to repeat, bien_lap is the variable that receives the value of each item inside chuoi_lap on each iteration. The loop will continue until it iterates to the last item in the string.

The for block is indented to distinguish the rest of the code.

Example 1:

#L?p ch? cái trong TipsMake
 for chu in 'tipsmake': 
 print('Ch? cái hi?n t?i:', chu) 
 #L?p t? trong chu?i 
 chuoi = ['b?','m?','em'] 
 for tu in chuoi: 
 print('Anh yêu', tu)

We have the following output:

Ch? cái hi?n t?i: q
Ch? cái hi?n t?i: u
Ch? cái hi?n t?i: a
Ch? cái hi?n t?i: n
Ch? cái hi?n t?i: t
Ch? cái hi?n t?i: r
Ch? cái hi?n t?i: i
Ch? cái hi?n t?i: m
Ch? cái hi?n t?i: a
Ch? cái hi?n t?i: n
Ch? cái hi?n t?i: g
Anh yêu b?
Anh yêu m?
Anh yêu em

Example 2:

# Tính t?ng t?t c? các s? trong danh sách A
# Danh sách A 
 A = [1, 3, 5, 9, 11, 2, 6, 8, 10]
# Bi?n ?? l?u tr? t?ng các s? là tong, gán giá tr? ban ??u b?ng 0 
 tong = 0
# Vòng l?p for, a là bi?n l?p 
 for a in A: 
 tong = tong+a
# ??u ra: T?ng các s? là 55 
 print("T?ng các s? là", tong)

When running the above code, you will get the result:

The total number is 55

Function Range ()()

You can use the range () function to create a sequence of numbers. For example, range (100) will create a number range from 0 to 99 (100 numbers).

The range function (start number, end number, distance between two numbers) is used to create a custom number sequence. If you do not set a distance between two numbers, Python will understand that it is equal to 1 by default.

The range () function does not store all the values in memory but stores the start value, the end value and the distance between the two numbers resulting in the next number in the sequence.

In order for range () to output all values, you need to use the list () function like the example below:

#L?nh 1 
 print(range(9)) 
 #L?nh 2
print(list(range(9))) 
 #L?nh 3
print(list(range(2, 5))) 
 #L?nh 4
print(list(range(0, 15, 5)))

We will have the following output:

range(0, 9)
[0, 1, 2, 3, 4, 5, 6, 7, 8]
[2, 3, 4]
[0, 5, 10]

Each line corresponds to Orders 1, 2, 3, 4 above.

The range () function can be used in conjunction with len () to loop through an array using index, as in the example below:

Example 3:

chuoi = ['b?','m?','em']

for tu in range(len(chuoi)):

 print("Anh yêu",chuoi[tu])

We have the same output as example 1 above:

Anh yêu b?
Anh yêu m?
Anh yêu em

Combine for with Else

In the previous lesson, you saw if. Else and if. Elif. Else. Else can not only combine with if, but in for loop can also be used.

In for, the else block of statements will be executed when the items in the string have been repeated.

Example 4:

B = [0, 2, 4, 5]

for b in B:
 print(b)
else:
 print("?ã h?t s?.")

Here, the for loop will print list B until the entries are gone. When the loop ends it executes else's block and prints. We have the result after running the code as follows:

0
2
4
5
?ã h?t s?.

The break command can be used to stop the for loop, and the else part will be ignored. In other words, the else part for for will run when no break is executed.

Example 5:

#L?p dãy t? 0 ??n 10 
 for num in range(0,10): 
 # Repeat on factors of a number in the sequence 
 for i in range(2,num): 
 #Xác ??nh th?a s? ??u tiên (phép chia có s? d? b?ng 0)
 if num%i == 0:
 j=num/i #??c l??ng th?a s? th? 2
 print ('%d b?ng %d * %d' % (num,i,j))
 break #D?ng vòng for hi?n t?i, chuy?n ??n s? ti?p theo trong vòng for ??u tiên
 else: # Ph?n else trong vòng l?p
 print (num, 'là s? nguyên t?')

The above code repeats the numbers in the range from 0 to 10, with each number running the loop to check if it is a prime number, if it is, print the message and stop the test loop, switch to the next number within First iteration, if not a prime number, then execute another else block. Running the above code we have the following result:

0 là s? nguyên t?
1 là s? nguyên t?
2 là s? nguyên t?
3 là s? nguyên t?
4 b?ng 2 * 2
5 là s? nguyên t?
6 b?ng 2 * 3
7 là s? nguyên t?
8 b?ng 2 * 4
9 b?ng 3 * 3

Above is the most basic knowledge about for loop, in the next article, you will learn about while loop, do you still remember where it was in the introduction series of Python TipsMake. Com?

Next article: While loop in Python

Previous lesson: if, if. Else, if. Elif. Else in Python