Scripting

# How to Iterate Through a List in Python A list is an ordered combination of different types of elements. There are several ways through which we can iterate over a list. The methods we‘ll discuss are as follows:

1. Using for Loop
2. Using the range () method
3. Using while loop
4. Using List Comprehension
5. Using enumerate () method
6. Using the NumPy module function

## Using for loop

By using for loop we can easily iterate elements of a list. Let’s consider this by an example given below.

```nl= [10, 20, 30, 40, 50, 60]

print("list items are as follows:")

for i in nl:

print(i)```

Output:

list items are as follows:

10

20

30

40

50

60 Output: In figure 1 we have used for loop to iterate list items containing numbers. The print function displays all elements of the list accessed by for loop as shown in figure 2.

## Using range() method:

In this method, we use the range function in combination with for loop. Let’s consider this by the example given below.

```nl= [10, 20, 30, 40, 50, 60]

for i in range(len(nl)):

print("list item",i, "is:",nl[i])```

Output:

list item 0 is: 10

list item 1 is: 20

list item 2 is: 30

list item 3 is: 40

list item 4 is: 50

list item 5 is: 60 Output: In figure 3 range function is used and the length of the list is given as a stop parameter for the range function. Figure 4 tells that every element is displayed with an index as output.

## Using while Loop

While loop can also be used to iterate list elements. Let’s consider this by example given below.

```wk_days = ["Monday", "Tuesday", "Wednesday", "Thursday","Friday"]

i = 0

while i < len(wk_days):

print(wk_days[i])

i = i + 1```

Output:

Monday

Tuesday

Wednesday

Thursday

Friday Output: In the above figure 5, we have a list of weekdays. While loop compares the length of the list with variable i and prints days name one by one as shown in figure 6.

## Using List Comprehension

In this method, we‘ll use List comprehension. It is the shortest and most tricky way. Let’s consider this by the example given below.

```ns_list = [10, "ten", 20, "twenty", 30, "thirty", 40, "forty"]

[print(n) for n in ns_list]```

Output:

10

ten

20

twenty

30

thirty

40

forty Output: In figure 7 we have a list containing string integers and strings. We can iterate the list items as shown in figure 8.

## Using enumerate() method

```alist = [1, 'number', 1.0, 'float', 'a', 'string']

for index, value in enumerate(alist):

print(index, ":", value)```

Output:

0 : 1

1 : number

2 : 1.0

3 : float

4 : a

5 : string Output: In figure 9 we have used enumerate function which displays the index number and value. We get output as shown in figure 10.

## Using the numpy module function

```import numpy as np

new_list = np.array([1, 'number', 1.0, 'float', 'a', 'string'])

for x in np.nditer(new_list):

print(x)```

Output:

1

number

1.0

float

a

string Output: To use the NumPy functions first thing we do is import the NumPy module. NumPy module has nditer() function that iterates the elements of the list.