Lists in Python - Practice 1

List syntax:¶

In [41]:

#Simple List :
team = ["sachin", "dhoni","ganguly"]
print(team)

['sachin', 'dhoni', 'ganguly']

In [42]:

#List of lists
temp = [[1,2,3,4],["a","b","c"],["A","B","C"],[1.0,2.0,3.0]]
print(temp)

[[1, 2, 3, 4], ['a', 'b', 'c'], ['A', 'B', 'C'], [1.0, 2.0, 3.0]]

Assessing List Elements by its index position¶

In [43]:

# To get sachin name:
sachin_name = team[0]
print(sachin_name)

sachin

In [44]:

# Getting "A" character from the temp variable
print(temp[2][0])

A

Negative Indexes¶

We can also use negative indexes in python, which counts from backwards starting -1. Index -1 refers the last element in the list

In [45]:

#printing last element from the "team" list
print(team[-1])

ganguly

Slicing the list values using index¶

We can slice a list by using list[start:end] syntax. It returns the list values from the start index and a value before end. It doesn't include the end index. For example, to get the name "sachin", and "dhoni" from the team list, we use the following code

In [46]:

print(team[0:2])

['sachin', 'dhoni']

Note: Index returns a single value. In contrast, slice returns a new list.

In [47]:

print(team[:])
print(team[:2])
print(team[1:])
new_team = team
print(team[:] == team)
print(team[:] is team)
print(new_team[:] is team)
print(new_team is team)

['sachin', 'dhoni', 'ganguly']
['sachin', 'dhoni']
['dhoni', 'ganguly']
True
False
False
True

Changing/Re-assigning a list value¶

In [48]:

print(team)
team[2] = "dravid"
print(team)

['sachin', 'dhoni', 'ganguly']
['sachin', 'dhoni', 'dravid']

Note : We can also use slice to change multiple values.

In [49]:

print(team)
team[0:2] = ["yuvraj","nehra"]
print(team)

['sachin', 'dhoni', 'dravid']
['yuvraj', 'nehra', 'dravid']

Deleting a value from a list¶

In [50]:

del team[1] # removes index 1 from the list
print(team)

['yuvraj', 'dravid']

In [51]:

#Few more operations
print("a" +"b")
print([1,2,3] + [4,5,6])
print("arun" * 3)
print([1,2,3]*3)

ab
[1, 2, 3, 4, 5, 6]
arunarunarun
[1, 2, 3, 1, 2, 3, 1, 2, 3]

List function.¶

This converts the values to a list

In [53]:

print(list("hello"))

['h', 'e', 'l', 'l', 'o']

Finding a value in a list¶

We can use "in" , "not in" to check whether a value is available in a list or not

In [54]:

print("a" in ["a","b","c"])
print("d" not in ["a","b","c"])

True
True

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