Need to add excerpt in recent post WP widget - wordpress

Question

I'm using a premium theme on my wp website but I'm trying to add a recent post widget on home page sidebar, this widget just shows posts title and date but no excerpt. I am a beginner don't know how to customize this widget, I just think these are the codes of the recent post widget.
<?php
/*-----------------------------------------------------------------------------------
Plugin Name: Custom Blog Widget
Plugin URI: http://www.premiumpixels.com
Description: A widget that allows the display of blog posts.
Version: 1.0
Author: Orman Clark
Author URI: http://www.premiumpixels.com
-----------------------------------------------------------------------------------*/
// Add function to widgets_init that'll load our widget.
add_action( 'widgets_init', 'tz_blog_widgets' );
// Register widget.
function tz_blog_widgets() {
register_widget( 'TZ_Blog_Widget' );
}
// Widget class.
class tz_blog_widget extends WP_Widget {
/*-----------------------------------------------------------------------------------*/
/* Widget Setup
/*-----------------------------------------------------------------------------------*/
function __construct() {
/* Widget settings. */
$widget_ops = array( 'classname' => 'tz_blog_widget', 'description' => __('A widget that displays your latest posts with a short excerpt.', 'Creativo') );
/* Widget control settings. */
$control_ops = array( 'width' => 300, 'height' => 350, 'id_base' => 'tz_blog_widget' );
/* Create the widget. */
parent::__construct( 'tz_blog_widget', __('Custom Recent Posts Widget', 'Creativo'), $widget_ops, $control_ops );
//$this->WP_Widget( 'tz_blog_widget', __('Custom Recent Posts Widget', 'Creativo'), $widget_ops, $control_ops );
}
/*-----------------------------------------------------------------------------------*/
/* Display Widget
/*-----------------------------------------------------------------------------------*/
function widget( $args, $instance ) {
extract( $args );
$title = apply_filters('widget_title', $instance['title'] );
/* Our variables from the widget settings. */
$number = $instance['number'];
/* Before widget (defined by themes). */
echo $before_widget;
/* Display Widget */
?>
<?php /* Display the widget title if one was input (before and after defined by themes). */
if ( $title )
echo $before_title . $title . $after_title;
?>
<?php
$query = new WP_Query();
$query->query( array(
'posts_per_page' => $number,
'ignore_sticky_posts' => 1
));
?>
<?php if ($query->have_posts()) : while ($query->have_posts()) : $query->the_post(); ?>
<div class="latest-posts">
<?php
if ( (function_exists('has_post_thumbnail')) && (has_post_thumbnail()) ) { ?>
<div class="latest-posts-thumb"><?php the_post_thumbnail('related-img'); ?></div>
<h2><?php the_title(); ?></h2>
<span><?php the_time( get_option('date_format') ); ?></span>
<div class="clr"></div>
<?php
}
else{?>
<div class="latest-posts-thumb"><img src="<?php bloginfo( 'template_url' ); ?>/images/no-image.jpg" /></div>
<h2><?php the_title(); ?></h2>
<span><?php the_time( get_option('date_format') ); ?></span>
<div class="clr"></div>
<?php
}
?>
</div>
<?php endwhile; endif; ?>
<?php wp_reset_query(); ?>
<?php
/* After widget (defined by themes). */
echo $after_widget;
}
/*-----------------------------------------------------------------------------------*/
/* Update Widget
/*-----------------------------------------------------------------------------------*/
function update( $new_instance, $old_instance ) {
$instance = $old_instance;
/* Strip tags to remove HTML (important for text inputs). */
$instance['title'] = strip_tags( $new_instance['title'] );
$instance['number'] = strip_tags( $new_instance['number'] );
/* No need to strip tags for.. */
return $instance;
}
/*-----------------------------------------------------------------------------------*/
/* Widget Settings
/*-----------------------------------------------------------------------------------*/
function form( $instance ) {
/* Set up some default widget settings. */
$defaults = array(
'title' => __('Take a look behind the scenes.','Creativo'),
'number' => 4
);
$instance = wp_parse_args( (array) $instance, $defaults ); ?>
<!-- Widget Title: Text Input -->
<p>
<label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e('Title:', 'Creativo') ?></label>
<input type="text" class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" value="<?php echo $instance['title']; ?>" />
</p>
<!-- Widget Title: Text Input -->
<p>
<label for="<?php echo $this->get_field_id( 'number' ); ?>"><?php _e('Amount to show:', 'Creativo') ?></label>
<input type="text" class="widefat" id="<?php echo $this->get_field_id( 'number' ); ?>" name="<?php echo $this->get_field_name( 'number' ); ?>" value="<?php echo $instance['number']; ?>" />
</p>
<?php
}
}
?>

Answer 1

//change this
if ((function_exists('has_post_thumbnail')) && (has_post_thumbnail())) { ?>
<div class="latest-posts-thumb"><?php the_post_thumbnail('related-img'); ?></div>
<h2><?php the_title(); ?></h2>
<span><?php the_time(get_option('date_format')); ?></span>
<div class="clr"></div>
<?php
}
//to
if ((function_exists('has_post_thumbnail')) && (has_post_thumbnail())) { ?>
<div class="latest-posts-thumb"><?php the_post_thumbnail('related-img'); ?></div>
<h2><?php the_title(); ?></h2>
<p class="post-excerpt"><?php the_excerpt(); ?></p>
<span><?php the_time(get_option('date_format')); ?></span>
<div class="clr"></div>
<?php
}
the_excerpt() is used to get post excerpt