CODEWITHSUNDEEP
pythonfor-loop
Data Beginner
Data Beginner

Reputation: 61

problems with extract relevant element from list using Python

I am a beginner with Python. I recently learned using loops and want to further improve my skills on it.

However, when I try to execute a for loop, the loop returns nothing. The loop itself is trying to extract any element that contains more than 2es, which should return Steven and De Gea.

all_data = [['John','Steven','Mosh'],
           ['Juan','Mata','De Gea']]

names = []

for y in all_data:
    if y.count("e")>=2:
        names.append(y)
names

Could someone kindly point out where I did wrong, much appreciate it.

Upvotes: 1

Views: 42

Answers (2)

Akshay Sehgal
Akshay Sehgal

Reputation: 19322

The problem is that your loop is iterating over a list of lists and not a flat list.

This means that in your for loop, y takes the value of a list. Printing y makes it clear. What you want to do is to iterate over y again to do check if the condition is met and add the same string to names.

for y in all_data:
    print(y)           #<--------
    if y.count("e")>=2:
        names.append(y)

['John', 'Steven', 'Mosh'] #<-------
['Juan', 'Mata', 'De Gea'] #<------

A working solution (with clearer variable naming) would be -

all_data = [['John','Steven','Mosh'],
           ['Juan','Mata','De Gea']]

names = []

for sublist in all_data:
    for string in sublist:
        if string.count("e")>=2:
            names.append(string)
names

['Steven', 'De Gea']

Here is a one-liner list comprehension for the same. Ill let you figure out how this is exactly the same as the above nested loop :) -

[string for sublist in all_data for string in sublist if string.count("e")>=2]

['Steven', 'De Gea']

Upvotes: 3

Schokotux
Schokotux

Reputation: 24

Working code:

all_data = [['John','Steven','Mosh'],
           ['Juan','Mata','De Gea']]

names = []

for y in all_data:
    for x in y:
        if x.count("e")>=2:
            names.append(x)
names

To find out why your code doesn't work try print('y') in your for loop to see what y iterates over.

Your code example would work if your array was all_data = [['John','Steven','Mosh', 'Juan','Mata','De Gea'] .

Upvotes: 0

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