Shikha Mishra

How to get First Key in a Dictionary Python: In this tutorial, we will discuss different ways to get the first key in a dictionary. Later, we will see & learn how to choose the first N Keys of a dictionary in Python.

• Get the first key from a dictionary using keys() method
• Get first key in a dictionary using iter() & next()
• Get the First Key in Dictionary Using list() Function
• Get the First Key in Dictionary Using for Loop
• Get first N keys from a Dictionary in Python

Get the first key from a dictionary using keys() method

Python print first item in dictionary: Dictionary stores elements in key-value pairs.Dictionary act as a container in python. Dictionary provided keys() function which we will use to fetch all keys in it and after that we select the first key from a sequence.

# Dictionary of string and int
word_freq = {
    'Anni': 56,
    "is": 23,
    'my': 43,
    'Fav': 78,
    'Person': 11
}
# Get the first key in a dictionary
first_key = list(word_freq.keys())[0]
print('First Key of dictionary:')
print(first_key)

Output:

First Key of dictionary:
Anni

Get first element of dictionary python: In the above example, you can see that first we have fetched all dictionary elements and by using indexing we find out the first key value.

Do Refer:

• Python Dictionary
• Python: How to find keys by value in dictionary?

Here is another way to do the same,

Another Way for How to get First Key in Dictionary Python

Print keys of dictionary python: By using this method, it will convert all keys of the dictionary to a list and then we can select the first element from the list.

# Dictionary of string and int
word_freq = {
    'Anni': 56,
    "is": 23,
    'my': 43,
    'Fav': 78,
    'Person': 11
}
# Get the first ket in a dictionary
first_key = list(word_freq)[0]
print('First Key of dictionary:')
print(first_key)

Output:

First Key of dictionary:
Anni

In the above example, we didn’t call the keys() function. We created a list of keys from the dictionary and selected the first item from it.

• Intersection of Two Dictionaries via Keys in Python
• Python Program to Sum All the Items in a Dictionary
• Python Program to Add a Key, Value Pair to the Dictionary

Get first key in a dictionary using iter() & next()

What we have done above that was not a perfect solution because first, we created a list and then fetch the first key in a dictionary. It is very difficult to apply that method in a large number of dictionaries. First, we iterate the object of keys using the iter() function then we apply the next() function on it for getting the first element.

This is an efficient solution because didn’t iterate over all the keys in a dictionary, we just selected the first one.

# Dictionary of string and int
word_freq = {
    'Anni': 56,
    "is": 23,
    'my': 43,
    'Fav': 78,
    'Person': 11
}
# Get the first key in a dictionary
first_key = next(iter(word_freq))
print('First Key of dictionary:')
print(first_key)

Output:

First Key of dictionary:
Anni

Get the First Key in Dictionary Using list() Function

Also, there is a possible way to convert the dict type into a list using thelist() function at first and later get the first key at the 0th index of the dictionary.

my_dict = { 'Russia': 2, 'New York': 1, 'Lahore': 6, 'Tokyo': 11}

print(list(my_dict.keys())[0])

Result:

Russia

Get the First Key in Dictionary Using for Loop

One more easiest way to get the initial key in a dictionary is using theforloop. After getting the first key of the dictionary break the loop.

Let’s see an example on it:

my_dict = { 'London': 2, 'New York': 1, 'Lahore': 6, 'Tokyo': 11}

for key, value in my_dict.items():
  print(key)
  break

Output:

London

Get first N keys from a Dictionary in Python

To select the first N keys from a dictionary, convert the keys of a dictionary to a list and then select the first N entries from that. For example, let’s see how to select the first 3 keys from a dictionary,

# Dictionary of string and int
word_freq = {
    'Anni': 56,
    "is": 23,
    'my': 43,
    'Fav': 78,
    'Person': 11
}
# Get the first ket in a dictionary
first_key = list(word_freq)[0]
print('First Key of dictionary:')
print(first_key)

Output:

First Key of dictionary:
Anni

Conclusion on Get First value in a dictionary of string and int

In this article, we have seen discuss different ways to find out the first key of a dictionary in python. All these dictionary keys methods in python help to find easily the key value in a dictionary of string and int word_freq. Get first key of the dictionary in python information completely from this article.

Python timestamp to string: In this tutorial, we will learn how to convert a timestamp string to a datetime object using datetime.strptime(). Also, you can understand how to to create a datetime object from a string in Python with examples below.

• String to a DateTime object using datetime.strptime()
• Format Code List
• How strptime() works?
• Examples of converting a Time String in the format codes using strptime() method

String to a DateTime object using datetime.strptime()

Python convert timestamp to string: Thestrptime()method generates a datetime object from the given string.

Datetime module provides a datetime class that has a method to convert string to a datetime object.

Syntax:

datetime.strptime(date_string, format)

So in the above syntax, you can see that it accepts a string containing a timestamp. It parses the string according to format codes and returns a datetime object created from it.

First import datetime class from datetime module to use this,

from datetime import datetime

Also Read:

• Python: How to remove characters from a string by Index?
• Convert integer to string in Python

Complete Format Code List

• Python Program to Find the Number of Weeks between two Dates
• Python Program to Calculate Age in Days from Date of Birth
• Python program to convert seconds into day, hours, minutes and seconds

How strptime() works?

In thestrptime()class method, it takes two arguments:

• string (that be converted to datetime)
• format code

In the accordance with the string and format code used, the method returns its equivalent datetime object.

Let’s see the following example, to understand how it works:

where,

%d – Represents the day of the month. Example: 01, 02, …, 31
%B – Month’s name in full. Example: January, February etc.
%Y – Year in four digits. Example: 2018, 2019 etc.

Examples of converting a Time String in the format codes using strptime() method

Timestamp to string python: Just have a look at the few examples on how to convert timestamp string to a datetime object using datetime.strptime() in Python and gain enough knowledge on it.

Example 1:

Let’s take an example,

from datetime import datetime
datetimeObj = datetime.strptime('2021-05-17T15::11::45.456777', '%Y-%m-%dT%H::%M::%S.%f')
print(datetimeObj)
print(type(datetimeObj))

Output:

2021-05-17 15:11:45.456777
<class 'datetime.datetime'>

So in the above example, you can see that we have converted a time string in the format “YYYY-MM-DDTHH::MM::SS.MICROS” to a DateTime object.

Let’s take another example,

Example 2:

from datetime import datetime
datetimeObj = datetime.strptime('17/May/2021 14:12:22', '%d/%b/%Y %H:%M:%S')
print(datetimeObj)
print(type(datetimeObj))

Output:

2021-05-17 14:12:22
<class 'datetime.datetime'>

So this is the other way to show timestamp here we have converted a time string in the format “DD/MM/YYYY HH::MM::SS” to a datetime object.

Example 3:

If we want to show the only date in this format “DD MMM YYYY”. We do like this,

from datetime import datetime
datetimeObj = datetime.strptime('17 May 2021', '%d %b %Y')
# Get the date object from datetime object
dateObj = datetimeObj.date()
print(dateObj)
print(type(dateObj))

Output:

2021-05-17
<class 'datetime.date'>

Example 4:

So if we want to show only time “‘HH:MM:SS AP‘” in this format. We will do like that,

from datetime import datetime
datetimeObj = datetime.strptime('08:12:22 PM', '%I:%M:%S %p') 
# Get the time object from datetime object 
timeObj = datetimeObj.time()
print(timeObj) 
print(type(timeObj))

Output:

20:12:22
<class 'datetime.time'>

Example 5:

If we want to show our timestamp in text format. We will execute like that,

from datetime import datetime
textStr = "On January the 17th of 2021 meet me at 8 PM"
datetimeObj = datetime.strptime(textStr, "On %B the %dth of %Y meet me at %I %p")
print(datetimeObj)

Output:

2021-01-17 20:00:00

Conclusion:

So in the above tutorial, you can see that we have shown different methods of how to convert a timestamp string to a datetime object using datetime.strptime(). Thank you!

Pad string with spaces python: In this tutorial, we are going to discuss how to do padding of strings using zero, space, or some other character. Also, you can get complete knowledge of the methods used for padding strings in Python. So, let’s get started on learning How to pad strings with Zero, Space, or some other character.

• Types of Padding in Python
• 1. Left padding of string in Python
  • Left pad a string with space using string.rjust()
  • Left pad a string with some character using string.rjust()
• 2. Right padding of string in Python
  • Right pad a string with zeros using string.ljust()
  • Right pad a string with space using string.ljust()
  • Right pad a string with some character using string.ljust()

Types of Padding in Python

There are two types of padding:

1. Left padding
2. Right padding

1. Left padding of string in Python

Python pad string with spaces: Left padding means adding a given character on the left side of a string.

For Example – If we pad three zeros in string 6 i.e, ‘0006’, or if we pad three space in string i.e,’6′

numStr = "6"
print('Original String :', numStr)
# Left pad the string with 0 to make it's length 4
numStr = numStr.zfill(4)
print('Updated String :' , numStr)

Output:

Original String : 6
Updated String : 0006

So in the above example, we have used'string.zfill(s, width)'to pad a given string on the left with zeros (0).

Also Check:

• Convert integer to string in Python
• Convert Python String to Int

Left pad a string with space using string.rjust()

Python zero pad: In this, we are going to use string.rjust() to add space in a given string.

numStr = "6"
print('Original String :', numStr)
# Make string right justified of length 4 by padding 3 spaces to left
numStr = numStr.rjust(4, ' ')
print('Updated String :', numStr)

Output:

Original String : 6
Updated String :    6

• String Formatting in Python
• Python Program to Remove Punctuations From a String
• Python Interview Questions on Data Types and Their in-built Functions

Left pad a string with some character using string.rjust()

Python pad string: For adding any character to our string we will use string.rjust() and pass that character in it.

numStr = "6"
print('Original String :', numStr)
# Make string right justified of length 4 by padding 3 '-' to left
numStr = numStr.rjust(4, '-')
print('Updated String :', numStr)

Output:

Original String : 6
Updated String : ---6

2. Right padding of string in Python

Python pad string: Right padding means adding a given character on the right side of the string.

Example- If we have a number string i.e. “ram”. Now we want to convert this string of length 3 to a string of length 6 by,

• Right padding three zeros to the string i.e. “ram000”
• Right padding three-space to the string i.e. “ram “
• Right padding three characters to the string i.e. “ram—“

Right pad a string with zeros using string.ljust()

string.ljust() is used for padding a given character to the right of string to make its a length equal to the given width.

numStr = "67"
print('Original String :', numStr)
# Make string left justified of length 5 by padding 3 0s to the right of it
numStr = numStr.ljust(5, '0')
print('Updated String :', numStr)

Output:

Original String : 67
Updated String : 67000

Right pad a string with space using string.ljust()

In this, we will use string.ljust() to pad given character,

userName = "Shikha"
print('Original String :', userName)
# Make string left justified of length 7 by padding 3 spaces to the right of it
userName = userName.ljust(7, ' ')
print('Updated String :' , userName, 'is')

Here 3 spaces are padded to the right of the given string to make its length 9.

Output:

Original String : Shikha
Updated String : Shikha   is

Right pad a string with some character using string.ljust()

We can pass a character in string.ljust(s, width[, fillchar]) to right pad the given string by that passed character.

userName = "shikha"
print('Original String :', userName)
# Make string left justified of length 7 by padding 3 '-' to the right of it
userName = userName.ljust(7, '-')
print('Updated String :' , userName)

Output:

Here, three ‘-‘ are padded to the right of the given string to make its length 9.

Original String : shikha
Updated String : shikha---

Conclusion:

In this article, you have seen that how to do padding of strings using zero, space, or some other character.

Thank you!

Pandas add a column: In this tutorial, we are going to discuss different ways to add columns to the dataframe in pandas. Moreover, you can have an idea about the Pandas Add Column, Adding a new column to the existing DataFrame in Pandas and many more from the below explained various methods.

• Pandas Add Column
• Add column to dataframe in pandas using [] operator
• Add new column to DataFrame with same default value
• Add column based on another column
• Append column to dataFrame using assign() function
• Add a columns in DataFrame based on other column using lambda function
• Add new column to Dataframe using insert()
• Add a column to Dataframe by dictionary

Pandas Add Column

Pandas is one such data analytics library created explicitly for Python to implement data manipulation and data analysis. The Pandas library made of specific data structures and operations to deal with numerical tables, analyzing data, and work with time series.

Basically, there are three ways to add columns to pandas i.e., Using [] operator, using assign() function & using insert().

We will discuss it all one by one.

First, let’s create a dataframe object,

import pandas as pd
# List of Tuples
students = [('Rakesh', 34, 'Agra', 'India'),
            ('Rekha', 30, 'Pune', 'India'),
            ('Suhail', 31, 'Mumbai', 'India'),
            ('Neelam', 32, 'Bangalore', 'India'),
            ('Jay', 16, 'Bengal', 'India'),
            ('Mahak', 17, 'Varanasi', 'India')]
# Create a DataFrame object
df_obj = pd.DataFrame(students,
                      columns=['Name', 'Age', 'City', 'Country'],
                      index=['a', 'b', 'c', 'd', 'e', 'f'])
print(df_obj )

Output:

    Name    Age  City        Country
a  Rakesh  34     Agra        India
b  Rekha   30     Pune        India
c  Suhail    31    Mumbai   India
d  Neelam 32   Bangalore India
e  Jay         16   Bengal      India
f  Mahak    17  Varanasi     India

Do Check:

• Pandas: Delete last column of dataframe in python
• Pandas: Loop or Iterate over all or certain columns of a dataframe

Add column to dataframe in pandas using [] operator

import pandas as pd
# List of Tuples
students = [('Rakesh', 34, 'Agra', 'India'),
            ('Rekha', 30, 'Pune', 'India'),
            ('Suhail', 31, 'Mumbai', 'India'),
            ('Neelam', 32, 'Bangalore', 'India'),
            ('Jay', 16, 'Bengal', 'India'),
            ('Mahak', 17, 'Varanasi', 'India')]
# Create a DataFrame object
df_obj = pd.DataFrame(students,
                      columns=['Name', 'Age', 'City', 'Country'],
                      index=['a', 'b', 'c', 'd', 'e', 'f'])

# Add column with Name Score
df_obj['Score'] = [10, 20, 45, 33, 22, 11]
print(df_obj )

Output:

      Name     Age   City        Country   Score
a    Rakesh    34    Agra          India      10
b    Rekha     30    Pune          India      20
c    Suhail     31     Mumbai    India      45
d    Neelam  32    Bangalore  India      33
e    Jay         16     Bengal       India      22
f    Mahak    17    Varanasi     India       11

So in the above example, you have seen we have added one extra column ‘score’ in our dataframe. So in this, we add a new column to Dataframe with Values in the list. In the above dataframe, there is no column name ‘score’ that’s why it added if there is any column with the same name that already exists then it will replace all its values.

• Pandas : Merge Dataframes on specific columns or on index in Python – Part 2
• How to convert Dataframe column type from string to date time
• Pandas : Change data type of single or multiple columns of Dataframe in Python

Add new column to DataFrame with same default value

import pandas as pd
# List of Tuples
students = [('Rakesh', 34, 'Agra', 'India'),
            ('Rekha', 30, 'Pune', 'India'),
            ('Suhail', 31, 'Mumbai', 'India'),
            ('Neelam', 32, 'Bangalore', 'India'),
            ('Jay', 16, 'Bengal', 'India'),
            ('Mahak', 17, 'Varanasi', 'India')]
# Create a DataFrame object
df_obj = pd.DataFrame(students,
                      columns=['Name', 'Age', 'City', 'Country'],
                      index=['a', 'b', 'c', 'd', 'e', 'f'])

df_obj['Total'] = 100
print(df_obj)

Output:

         Name    Age    City     Country      Total
a       Rakesh   34    Agra       India          100
b       Rekha    30    Pune       India          100
c       Suhail     31   Mumbai  India          100
d       Neelam  32  Bangalore India        100
e       Jay          16  Bengal       India        100
f       Mahak     17 Varanasi     India        100

So in the above example, we have added a new column ‘Total’ with the same value of 100 in each index.

Add column based on another column

Let’s add a new column ‘Percentage‘ where entrance at each index will be added by the values in other columns at that index i.e.,

df_obj['Percentage'] = (df_obj['Marks'] / df_obj['Total']) * 100
df_obj

Output:

    Name  Age       City    Country  Marks  Total  Percentage
a   jack   34     Sydeny  Australia     10     50        20.0
b   Riti   30      Delhi      India     20     50        40.0
c  Vikas   31     Mumbai      India     45     50        90.0
d  Neelu   32  Bangalore      India     33     50        66.0
e   John   16   New York         US     22     50        44.0
f   Mike   17  las vegas         US     11     50        22.0

Append column to dataFrame using assign() function

So for this, we are going to use the same dataframe which we have created in starting.

Syntax:

DataFrame.assign(**kwargs)

Let’s add columns in DataFrame using assign().

import pandas as pd
# List of Tuples
students = [('Rakesh', 34, 'Agra', 'India'),
            ('Rekha', 30, 'Pune', 'India'),
            ('Suhail', 31, 'Mumbai', 'India'),
            ('Neelam', 32, 'Bangalore', 'India'),
            ('Jay', 16, 'Bengal', 'India'),
            ('Mahak', 17, 'Varanasi', 'India')]
# Create a DataFrame object
df_obj = pd.DataFrame(students,
                      columns=['Name', 'Age', 'City', 'Country'],
                      index=['a', 'b', 'c', 'd', 'e', 'f'])
mod_fd = df_obj.assign(Marks=[10, 20, 45, 33, 22, 11])
print(mod_fd)

Output:

It will return a new dataframe with a new column ‘Marks’ in that Dataframe. Values provided in the list will be used as column values.

Add column in DataFrame based on other column using lambda function

In this method using two existing columns i.e, score and total value we are going to create a new column i.e..’ percentage’.

import pandas as pd
# List of Tuples
students = [('Rakesh', 34, 'Agra', 'India'),
            ('Rekha', 30, 'Pune', 'India'),
            ('Suhail', 31, 'Mumbai', 'India'),
            ('Neelam', 32, 'Bangalore', 'India'),
            ('Jay', 16, 'Bengal', 'India'),
            ('Mahak', 17, 'Varanasi', 'India')]
# Create a DataFrame object
df_obj = pd.DataFrame(students, columns=['Name', 'Age', 'City', 'Country'],
                      index=['a', 'b', 'c', 'd', 'e', 'f'])
df_obj['Score'] = [10, 20, 45, 33, 22, 11]
df_obj['Total'] = 100
df_obj = df_obj.assign(Percentage=lambda x: (x['Score'] / x['Total']) * 100)
print(df_obj)

Output:

Add new column to Dataframe using insert()

import pandas as pd
# List of Tuples
students = [('Rakesh', 34, 'Agra', 'India'),
            ('Rekha', 30, 'Pune', 'India'),
            ('Suhail', 31, 'Mumbai', 'India'),
            ('Neelam', 32, 'Bangalore', 'India'),
            ('Jay', 16, 'Bengal', 'India'),
            ('Mahak', 17, 'Varanasi', 'India')]
# Create a DataFrame object
df_obj = pd.DataFrame(students, columns=['Name', 'Age', 'City', 'Country'],
                      index=['a', 'b', 'c', 'd', 'e', 'f'])
# Insert column at the 2nd position of Dataframe
df_obj.insert(2, "Marks", [10, 20, 45, 33, 22, 11], True)
print(df_obj)

Output:

In other examples, we have added a new column at the end of the dataframe, but in the above example, we insert a new column in between the other columns of the dataframe, then we can use the insert() function.

Add a column to Dataframe by dictionary

import pandas as pd
# List of Tuples
students = [('Rakesh', 34, 'Agra', 'India'),
            ('Rekha', 30, 'Pune', 'India'),
            ('Suhail', 31, 'Mumbai', 'India'),
            ('Neelam', 32, 'Bangalore', 'India'),
            ('Jay', 16, 'Bengal', 'India'),
            ('Mahak', 17, 'Varanasi', 'India')]
# Create a DataFrame object
df_obj = pd.DataFrame(students, columns=['Name', 'Age', 'City', 'Country'],
                      index=['a', 'b', 'c', 'd', 'e', 'f'])
ids = [11, 12, 13, 14, 15, 16]
# Provide 'ID' as the column name and for values provide dictionary
df_obj['ID'] = dict(zip(ids, df_obj['Name']))
print(df_obj)

Output:

Want to expert in the python programming language? Exploring Python Data Analysis using Pandas tutorial changes your knowledge from basic to advance level in python concepts.

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